Changing gender = not a big deal (for me) and in of itself doesn't demystify or ruin anything.
Especially if they give the characterization some oompf and Chibnall putting far more charisma, backstory, detail... even care?!... into his throwaway incarnation in series 12 than he did for Jodie, the full time and the true throwaway edition as crafted solely by Chibnall, is telling regarding how much he must frothing hate the show. He's not just writer or even head writer but main showrunner. This is 100% his crafting for the series now. The only thing arguably worse is if Doctor Ruth was as horrendously scripted, yet not only wasn't she not badly scripted (good to excellent depending on scene), there's a far more interesting arc (temporal paradox aside)... Which then got revealed in a completely unimaginable way yet not in a good way at the same time.
Deconstructing the origins by saying the Doctor is no longer a maverick off-the-wall renegade (not just as the more common definition of "a joke teller") of her/his own people but is from another magical universe and dimension and popped into ours is cringeworthy all on its own, but having the Gallifreyans engage in the ultimate IP theft with the magical being's DNA via mass murder on top of all that... Which leads to a dichotomy. The first half, the good news, is that the Doctor still is the maverick ((but they can play "universe hopscotch" forevermore and nobody's going to give a toss, especially given how badly Chibnall did it - "the Master programmed a lie into the Matrix" pretty much undoes Chibnall's whole scheme in seconds in a surprisingly less cringeworthy manner, albeit not by much.)) The other half, the bad half, is that Mary Whitehouse would be spinning in her grave and she'd probably be right. At least Chibnall outdid Eric Saward, and by an impressive distance, in using crudity as a plot crutch. At least Saward's era had more depth and less cynicism... is Chibnall trying to give the mid-80s a boost?
One thing's for certain - the complaint of "too many companions" doesn't hold up when shows like "Sliders" made having ensembles of four work.
I would have preferred a female galifrayian being introduced into the show and playing off the Doctor. Than eventually getting her own show either as a traveling time lord or maybe an all together different mission from what the Doctor pursues.
Oh well Lost Chances.