The revelation nobody wanted

In some ways the revelation of the Doctor being the Timeless Child, cast adrift from some alternative dimension and not just another Time Lord from Gallifrey, hasn't actually changed very much. It plugs the continuity point from The Brain of Morbius and goes some ways to explaining why the Doctor has never been quite like any other Time Lord. Up until The War Games we knew nothing about the character save that they came from another planet, although early writers presented the Doctor more as a time traveller than a space adventurer. The emphasis was more on him coming from the future rather than being an alien. He sometimes described himself in human terms, and only appeared to have one heart.
Susan claimed to have named the TARDIS, and several times the Doctor seemed to suggest that he had built the ship himself. Things started to change with the introduction of the Monk in The Time Meddler, when we saw that the TARDIS was not unique. The Doctor mentioned coming from a different time to the Monk ("50 years earlier"), again implying that time was more important to him than space.
More revelations followed, as we saw that the Doctor could renew his body when it grew too frail, and he would then tell Jamie and Victoria that he was around 450 years old in Earth terms.
The War Games finally gave us the Doctor's backstory. He was a Time Lord from another planet, one of a race of people who were almost immortal barring accidents. He had stolen the TARDIS and set out to explore the universe, as the Time Lords preferred to merely observe and never interfere. He saw himself as a crusader as much as an explorer.
In the next story we learn of the two hearts and the other differences in his anatomy that make him only appear human.
Other details about the Time Lords followed, such as their use of the Doctor as an agent for intervention, when they couldn't be seen to interfere. We learned of Omega and how he gave the Time Lords the power needed to kickstart their time travel experiments. The Deadly Assassin then introduced Rassilon, and we saw that the Time Lords weren't such God-like beings after all. Beneath the facade they were just like us. We also learned that Time Lords could only regenerate 12 times, which told us that this was unlikely to be some purely biological process, but rather some product of genetic engineering, which is something that The Timeless Children has now confirmed.
So over the years we have always been drip-fed new information about the Doctor.
The problem is that we have never, ever wanted to know everything. Every time the mystery of the Doctor us revealed, the character has been diminished. Steven Moffat played around with the Doctor's name for more than a season, but he was never intending to ever reveal it. Back in the 80's Marc Platt proposed a story called "Lungbarrow" which would have taken the Doctor back to his ancestral home and revealed all sorts of details about his background as "the Other" who was a contemporary of Omega and Rassilon - an idea hinted at in Season 25. Everyone thought that Platt's idea was a stupid one, as revealing too much about the Doctor was a mistake. There may not be a question mark after Doctor Who but some sense of mystery about who they are and where they come from has always been part of the series' attraction.
No one really wanted to know any more about the Doctor's background. Enough had already been told, generally diminishing the character as I've said. The final two seasons of the Classic Era were specifically trying to put the mystery back into the series, rather than to remove it as too much had been revealed, and everyone agrees this was a good idea.
The Doctor was at his best when he was the mysterious traveller, origins unknown, who didn't even know how to pilot the TARDIS properly. A Doctor who was simply an explorer, but who fought injustice whenever he encountered it simply because it was the right thing to do.
When the series returned in 2005, Russell T Davies had done away with the Time Lords, making the Doctor the explorer once again. Moffat then bogged the character down in interminable story arcs and made the Doctor some kind of intergalactic celebrity, known to everyone, which was a huge mistake. He backtracked by then having the Doctor go round removing himself from every database.
Chibnall has decided to give the Doctor a whole new backstory - one which, like I've said, nobody was really asking for. If he wanted to divorce the Doctor further from the Time Lords and make the character more mysterious again then he's gone about it the wrong way. Far too much was given away about the Timeless Child. A better writer would have dropped hints and left it at that, allowing fans to speculate. The Master simply indulges in one massive info-dump of exposition. Surely there were better ways of revealing some of this through proper storytelling?
Does any of this really matter? Has Chibnall broken the programme?
Not really, as we've just seen how he has simply swapped one backstory for another, albeit in a terribly clumsy manner.
As always, when fans try to plug continuity gaps they just create new ones. The TARDIS Dr Ruth had shouldn't look like a Police Box. If the Timeless Child is such a significant figure for the Time Lords how did they come to lose him when he ran away from Gallifrey? Surely they would have kept him locked away to stop other races discovering his regenerative abilities.
At the end of the day, I don't really care who the Doctor is. I never have.
What's always been more important to me is what the Doctor does.
I had to laugh when I saw the cover of the new DWM due out on Thursday. "Jo Martin is the Doctor" it exclaims. No she isn't. She has done absolutely nothing to deserve that title. Just saying you're the Doctor and having a TARDIS means f*** all. Who the Doctor is, what their backstory is, it's all immaterial. It's what they do that counts. It's really sad that the current showrunner doesn't understand this.