If i were to be "optimistic" I would say the BBC's absolute least shit option in order to get a portion of its old viewers back would be
a) retcon retcon RETCON: sure its absolute cowardice but there is no way in hell the timeless child shit can be salvaged even when you separate it from the embarrasing wokesped shit that permeated the entire "the doctor is achtchully originally a little black refugee girl who the evil fffucking white time lords harvested for melanin to build their empire" concept. The only way to make it halfway workable would be for it to apply to anyone *but* the doctor and spin it as the master lying as usual.
b) backpedal like fucking crazy: having the doctor spend 2005-2013 perma miserable about wiping out his own race, barely finding a way to save them in the 50th anniversary special, and then just going "meh" when they are re-wiped because "they deserved it because the OG timelord leadership were evil n sheeit" as seems to be the case is as colossal a fuckup in characterisation as the timeless child was a fuckup in lore and continuity
c) moratorium on wokesped on and off screen: both in terms of "masturbating about how awesome and progressive you are on camera in order to get media asspats" and "trying to annoy people who say your attempts to crowbar in autistic political references suck" as both of these things have helped ensure an ever dwindling fandom rapidly became actively hateful of the show that was trying to spin lazy ass "racism am bad" style lectures on shit thats been the norm for half a century as edgy and brave and important moments in the show history and accusing anyone who called bullshit a nazi.
d) Stop taking such stupidly long fucking breaks between episodes and seasons and stop shaving the number of episodes: Having to wait upwards of a year between seasons and half a year between chunks of episodes without any set schedule or release date would be absolutely disastrous for even the best written and most beloved shows as people wont know when the fuck they can expect continuation and thus their interest will inevitably drift, and this goes doubly if they only randomly get to see 1-3 episodes in any given block. When the show sucks as much as it does however, it gives people just one more excuse not to bother watching.
e) stop using the fucking cybermen: for fuck sake I get there are probably some legal issues with the daleks still, but the cybermen have been overused past the point of embarrasment at this point, and in just about every appearence they have been absolute fucking garbage. retire them for 5 years or more until you can think of something worth doing with them.
and now the most controversial one, but hey this is my "optimistic for the show's future" take here, not my "optimistic for a show that wont still be trash on a fundamental level" take....
f) bring back david tennant as the doctor........really: Yes. I know. This is fucking stupid. This is the most desperate fucking pandering the show could ever pull. This is downright fucking pathetic. I know, I know. But again this is me trying to have an "optimistic take" for the show not being cancelled again going forwards even if I really fucking want it to be cancelled myself.
Basically david tennant is still "the face" of nu-who and is still fawned over by tumblr heffers, reminisced over nostalgically by zoomers, not hated too much by old fans, and is generally remembered positively by the wider viewing public in the role, and him being re-cast as the doctor would be one hell of a ratings stunt which could theoretically pay off long term if he was given decent scripts to work with to keep the interest going forwards.
And thanks to the aforementioned 50th anniversary special, this has canonical precedent since there is a future tom baker doctor shown at the end.
Would any of this shit get me back in to the show?
Hell no.
It would still almost 100% certainly be absolute fucking trash writing and acting even if these most glaring issues were taken care of and it would almost certainly fuck up just as bad if not worse all over again because of the absolute retards the BBC likes to diversity/inclusion/nepotism hire.
However the first 3 things are what i have seen complained about the most by far on a real diverse array of online sauces, I believe making a big song and dance about solving them would probably be a start in getting some of the less embittered fanboys back on board, and throwing a bunch of pure fanboy chum into the water as disney has recently been doing with star wars has some vague chance of turning shit slightly around assuming they get both good press from the usual media goons *and also* positive reactions from traditionally negative voices which may be enough to cause positive word of mouth to begin making a difference......
....but honestly even if they pull all this shit off I strongly suspect it will still fail to bring back those who stopped watching and the show will be cancelled shortly afterwards either way.