Much like the show in the latter years of its first run it collapsed under the weight of its own canon, and writers/showrunners that enthusiastically embraced that canon and alienated the casual audience.
IMO they should never have brought back the Time Lords. That was the genius stroke of the 2005 reboot. Just make the Doctor an intergalactic oddball, let the adventures run from there. What's weird is that Russell Davies was the one who understood this... then when he came back to the show he shoveled nostalgia on top of nostalgia and sank the thing.
I never even watched the Chibnall era so I'm not fully informed but from reading about the Timeless Child arc it just sounds like a show disappearing up its own arse. It's supposed to be a family show, younger kids don't care about that kind of stuff. Just make it fun.