People aren't missing your point, they just don't agree with it.
You're saying that filmmakers and studios should pander to a small but vocal subset of audiences that resent casting anyone who is not a straight white male in the lead role even if there is no compelling storytelling reason not to do so, just to avoid their complaints, and the appearance of having an "agenda". The agenda apparently being acknowledging that people other than straight white males can be the hero of a film.
But if you give in to their demands, what reason will they have to ever change what they're doing? They would be successfully influencing your filmmaking decisions with their bigotry. So a time where such complaints fade into irrelevance will only be postponed because you're actively encouraging it to continue by giving in to their irrational demands.
Can you imagine a Terminator film centered around a female lead who is being hunted because she's the mother of the future savior of humanity? What kind of agenda driven nonsense is that? Next thing you know, they'll want to make the lead character of the Alien films a woman too.