To be perfectly blunt, what the show actually is has been in constant flux between production teams and showrunners throughout the franchise's history, and nobody involved in making it truly care about whether past or future eras are consistent with each other or not. Lambert was fine with RTD (preferred him to JNT, in fact), Barry and Terrance liked John Simm as the Master. Hinchcliffe visited Chibnall on set, and praised RTD and Moffat. They had their time, and they're happy with others making the show into whatever they want so long as it continues to exist. As veterans of TV making, they understand that audiences change and the show changes to whatever the current producers think will appeal to them the most.
Robert Holmes was fine with completely rewriting the War Games, Terrance was fine with him doing it, neither would give a shit if any of their other creations were retconned to service future stories. They wrote some entertainment, their bosses told them it was good enough at the time and they got paid. Moffat completely shat on the Time War and RTD couldn't give a rat's ass either.
The "life and soul" of Doctor Who is an invention of the fans. Ian Levine is the only reason we don't have Silurians from the planet Siluria. And if we did, Briggs would just insert an audio drama explaining it and we'd move on.
Incredible, even after the Timeless Children and the shows viewers dropping to 2 million and it becoming an international joke as a result of the "no canon" bullshit, RTD supporters still learn NOTHING!
Okay first off, continuity is not some nerd obsession. It is a facet of story telling. You cannot actually tell a story without continuity! It's f*cking insane that I ever had to say that bit of common sense, never mind that I keep having to after I have been proven right again and again, and again, and again, and again. I feel like Jeff Goldblum in Jurassic World at this stage.
Yes the old series writers did care about continuity not because they were die hard fans, but because they were writing a story, and in order for it to be a story and not just a jumbled series of events they had to have continuity of some kind. If there was no continuity explain this to me.
Why does Vicki know the Daleks after they invaded earth in the 22nd century and she was said to come from after then? Why is the Doctor always trying to get Ian and Barbara home and insists they boarded their way into the ship? Why is the Daleks home planet always Skaro? Why does Patrick Troughton recognise the Daleks and the Cybermen and the Ice Warriors and the Yeti? Why does Jamie get sent back to the time period of the Highlanders and Zoe get sent back to the Wheel? Why does Victoria mention a Dalek killing her father? Why from Hartnell to McCoy is the Cybermen's home planet stated to be Mondas, and why is it always said to have been destroyed. (And don't say that Tomb retcons it to Telos, as it doesn't. Telos is explicitly said to be their adopted planet by the Cybermen themselves in the story. They say that after Mondas was destroyed, they attacked the Moonbase, and when that failed they fled to Telos.)
Why are the Thals always depicted as the other natives of Skaro? Why are the Ice Warriors from Mars? Why are the Doctors people always the Time Lords after they are introduced? Why is the 13 lives limit always in place after it is revealed? Why after Troughton is exiled does Jon Pertwee remain trapped for 3 years, until the Time Lords are shown to remove the exile?
Of course there was continuity. Yes there were a few blips, but there are continuity mistakes in every work of fiction. It's fine to get something small like Atlantis that isn't a big part of the lore, or a minor thing like the dates wrong, but big important things, like key characterisation, a characters origin, their motivation, no that matters if you want to have, what's the word? A story!
The so called changes that are often cited as proof that DW had no continuity are nothing of the sort. Revealing that the Doctor could regenerate, was filling a gap in, as we had no idea what his alien biology was like. Revealing that his people were the Time Lords, was similarly filling a gap in. We didn't know anything about his people prior to the War Games except that they were advanced and he was on the run from them. The War Games still fitted in with that. Similarly finding out he could only change 12 times? That was also filling a gap in. Nothing had been said other than a vague, one off comment about how Time Lords can practically live forever, which could have been just in comparison to humans.
This is why the Morbius Doctors is not the same thing as The Timeless Children. At that point we didn't know if Hartnell was the first Doctor or not. That was filling a gap in. Now personally I despise the idea of there being pre Hartnell doctors even in that context, but it wasn't the same in any way as what Chibbers did. I might add that at least Hinchcliff left it open ended, stating that he only intended to imply pre Hartnell Doctors.
The Deadly Assassin meanwhile was NOT a retcon. It doesn't even contradict the War Games. This all comes from ONE fan review, which I felt was based on incorrect memory. In the War Games the Time Lords have the death penalty and are willing to use torture, showing they are not an all peaceful race. The same is true in The Deadly Assassin. In both they have cut themselves off from the universe. In both they are so hung up on tradition that they care more about that than anything, (hence why they still exile the Doctor despite admitting he is a hero.)
Genesis of the Daleks is a retcon, and one of the few genuine ones, but even then no one is saying you can't ever do a retcon. A retcon is where you show us part of the story that we never knew existed before, but you still loosely make it fit with established continuity. Genesis does that. It uses the loophole of we never saw the actual creation of the Daleks, we only heard a vague, second hand account from someone hundreds of years later, and shows us it went slightly differently from what that told us. Even then it still follows the same basic story. IE in both Daleks come from Skaro, in both they started out as humanoid aliens who became locked in a war with the Thals, and in both cases the Thals were worse, and in both cases the war went atomic and destroyed the surface of the planet and caused both sides to mutate, with the Daleks humanoid ancestors degenerating into slimy octopus creatures who housed themselves in robot casings.
The only difference is now we learn Davros was involved, and I might add Davros actually fixes a bit of a plot hole in previous Dalek stories. Up until that story the Daleks had always been portrayed as completely single minded in their quest to conquer the galaxy and destroy or subjugate lesser life forms. There were never any heroic Daleks, or even self serving Daleks who didn't want to sacrifice themselves. That didn't make sense when they had originally been creatures like us, who had simply mutated. Genesis however explains that well, as Davros conditions them to be that way in Genesis.
Doctor Who's canon was not invented by the fans. It was there because it was a serious drama series, and therefore had to have it. What ironically was invented by the fans, was the myth that it had no canon. This was created by the Fitzroy Clique, the fandom incrowd made up of RTD, Mark Gatiss, Steven Moffat, Gary Russell, Nicholas Briggs who took over the franchise in the 90s and who from the start couldn't be arsed doing any research. They just thought they could wing it on their vague childhood memories and because everybody viewed DW in their snobby, upper middle class circle as a joke, nobody would care. However they were met with a backlash and so they invented the no canon bullshit, and cited individiual continuity blips, which again were minor to justify it.
Sadly the fandom was eventually duped as they were so insecure about the show, after it got the disgusting treatment from the mainstream media in the 90s, they were desperate for it to come back. The Fitzroy Crowd were also able to spread a lie that any adherence to continuity would result in dozens of references that would drive casual viewers away.
Now this approach worked during the RTD era at least at first, as it was introducing a whole new generation to the show who didn't know any better. (Obviously I am not saying the old one was forgotten and that it had no new fans. I myself was one, but obviously something on tv would reach more people than video releases.) On top of that even a lot of old fans were simply euphoric at having it back.
However very soon the no canon law began to turn in on new who itself, and hilariously the result of no continuity would always inevitibely be continuity porn, the very thing that it was supposed to stop.
The reason for that is that once you completely destroy something's identity, in order to convince people it is the same thing, you have to remind people it is the same thing by shoving in tons of member berries. This has happened again and again for New Who.
Missy, the single worst denigration of the character of the Master, a beloved icon, was followed by a member berries Dalek special with pointless clips of old stories and every dalek variant.
Casting a woman Doctor was followed by Barrowman being brought back for a pointless cameo.
The Timeless Children was followed by a finale with 8 previous Doctor and for the first time an old actor returning as the current Doctor!
In all cases if they'd just stuck to basic canon, IE Doctor is a time lord, Master is his archenemy, Doctor is an old, crazy uncle type mad professor, like a nice version of Rick, then they would have had to reference the past much less frequently and could have moved on in proper ways, new monsters, planets, stories, natural development for the Doctor.
Sadly however because of the cult of personality around RTD, people still buy into this crap. Let's just hope he goes the way of Joss Whedon soon.