I might have to disagree with some of what you say, though you perfectly got the answer right on one count. I think this dilutes the entire situation into a male problem. I don't think it is an issue with the male audience or readers.
We are in a time when we are open to ideas. There is a reason we see numerous BL, GL, and LGBTQ+ stories, many of them written my male authors and comic creators. It is because, as writers and storytellers, we are an open culture.
If I had to offer my feedback, then I think you nailed it when you mentioned that it is a power fantasy. That's literally it.
Take a look at isekai. It mainly includes a male protagonist who enters another realm an is absolutely powerful/intelligent. He goes from level 1 to level 100 (or breaks the level barrier) and defeats the bad guys in one fell swoop. That's to cater to male power fantasy.
At the same time, the villainess stories are sort of like the female version, where now the character is a female. She is absolutely powerful/intelligent and defeats the bad guys/controls people around her. That's to cater to the female power fantasy.
Don't misunderstand me. I'm not saying that it is a problem. There is nothing wrong in indulging in your fantasy and if you get an audience for that, then you are doing great. But it really isn't about the male audience and if people are using that as an excuse, it's merely to appeal to an audience, not because it is entirely true.
That doesn't mean such people don't exists. Are there people who feel threatened by female protagonists? Sure there are. But there are also female readers who like to label any story with a strong male protagonist as a sexist piece of fiction. We have crazy people on both sides. But they don't represent the majority and neither are they part of the main reasons.