No one knows why they chose a female Bond - there cannot be a female Bond. Please see my previous post about artists and intellectual property.
Just to spell it out, here's another example: the character of Rocky Balboa can only be an Italian-American man. Sly Stallone created the character and that's how he's written. In Rocky (1976) Apollo Creed says at the press conference:
Apollo - Hey Rock, my main man, come here. Ain't you Italian?
Rocky - Yeah, I'm Italian.
Random journalist - So what does that mean?
Apollo - It means, if he can't fight, I bet he can cook.
Also, Mickey calls Rocky a 'dumb Dago'.
So, Hollywood can't change Rocky Balboa. They could introduce a female boxer into the Rocky universe, perhaps.
Afterburn has it right - the new film is about a female 007. This shouldn't be a problem because there have been female heroes (there's a word for female heroes - heroines) in film for decades - see Ellen Ripley, Sarah Connor, Nancy Thompson, Trinity, Jackie Brown, etc. etc.
There could be an issue if the new 007 film is written poorly and identity politics is shoved down the audience's throats - see Ghostbusters (2016) and The Last Jedi (2017). I guess we'll just have to wait and see.