As a classic DW fan, I'm not crazy about the gender change either, but expected it as the calls for it were growing louder and louder in the last few years. (especially after the Master changed gender)
And the new era DW has been breaking so many bounderies and bringing in a lot of radical new concepts that the classic era would never have done (like allowing for wholesale deaths of innocents, just to be more "realistic"... but this is science FICTION - it was great because it wasn't real with including excessive killing, or torment and pain of named/known characters being killed off every episode).

Dr Who was something kids like me (and the generation before) would watch and be inspired to solve problems and use imagination, particularly if you lacked the physical aptitudes of your peers who treated you differently because of your intellect... it was an escape to feel like you related to a hero that was also intellectual. With the new era of DW dealing with gay (and now transgender) issues, it could give those people a hero to relate to as well.

This is something new, that I think fits in with the new era philosophy of DW, and as such, I'm willing to see how it will turn out.
If it doesn't appeal or work out, there is still 54 years of DW for those fans who don't like it, to fall back on.

And if they didn't do it eventually, the vocal elements of the fandom and clickbait media will keep badgering the writers and BBC until they do.