There's a theory (not original to me) that at the end of Trial of a Time Lord in 1986 (Colin Baker's last story) The Doctor did not escape The Matrix. If you watch the last two episodes (sometimes called The Ultimate Foe), there's at least one fake out where it looks like The Doctor is out of The Matrix and back in The Trial Room, but it's really an illusion in The Matrix. The traditional interpretation of the final episode is that shit blows up and stuff and The Doctor escapes The Matrix and then flies off in the TARDIS with a future version of Mel he hasn't met yet, which obviously makes no sense. It makes more sense if it was another illusion within The Matrix, and so has everything in the program since.
A continuation of the program under that premise could retcon so much nonsense and start with The Doctor escaping The Matrix. Literally everything in NuWho is just a Matrix illusion. It would retcon The Timeless Children and so much more. Remember Moffet's first season with Matt Smith when he resolved the series arc by having Ginger "reboot the universe" by remembering The Doctor? Does that seriously sound like an actual plot resolution or a Matrix illusion. Or when Bill saved the Earth by remembering her mother or something? Father's Day was a good episode, but since when are flying lizards eating time when something gets changed? Crazy things happen in The Matrix. Go back and watch Deadly Assassin and the end of Trial if you don't believe me. It's Clown World before Clown World was a thing.
I have good things I could say about McCoy through Capaldi, with Eccleston and Capaldi being the obvious standouts. But nothing has made sense in the show for a long time, even before Chinballs and Full ReTarD2. And they don't get thrown out. They were just Matrix Doctors. Kind of count, kind of don't. But with no impact on the story if The Doctor ever escapes The Matrix.
But it's such a serious change in canon that it's worth noting at least one thing that gets thrown out for each of these Doctors.
McCoy: Fenric was not really defeated by some Russian's faith in Communism. (Hi, Cartmel!)
McGann: Didn't really kiss that girl. Plus, not really half human.
Ecclestone: Didn't really kiss Captain Jack. Plus, didn't really suck up to the welfare state at the end of The Doctor Dances.
Tennant: Didn't really make a genetic daughter with Peter Davison called Jenny (Genny?) that he later married and had trans kids with.
Smith: Didn't marry Ginger's Time Daughter.
Capaldi: Didn't defeat "capitalism" in Oxygen even though he can never look at anything ever again because he's STILL BLIND. (But he can keep the sunglasses.)
I don't even have to justify the later "Doctors" but I feel compelled add:
Gatwa: Dindu nuffin.
Actually, while I'm at it, Colin didn't bump his head on the exercise bike and regenerate. And he didn't really say, "carrot juice, carrot juice, carrot juice."
All Matrix Clown World.
Colin Baker did try to strangle Peri though. We have to keep that.