Supergirl started as a nice show that was promoting female power, but at the 4th-5th season transgender and black women started to appear just becuase they are transgender and black, and men characters got dropped out of the show just because they are men even though they were very good team companions to supergirl.
Also for me it's boring to hear how much women don't need men instead of seeing an interesting story.
The other problem with subsequent seasons with lots of PC speech is that viewer counts drop because of the boring story line, and then of course the series gets cancelled.
That space force comedy with Steve Carell comes to mind
I don't think it's a political agenda. I think a sizeable portion of people just like seeing this stuff that affirms their beliefs or gives them an example to point to. Conservative leaning stuff does it too, and it's even more annoying when you disagree with its themes. I recall Logan Lucky (movie) was an especially aggravating example of this on the conservative side.
It's the difference between making a film about black Peter Parker vs. (black) Miles Morales for spider man. If they go for Miles, great, sounds like a good start. If they go for the former, you really have to wonder why, and how big of a deal its going to be. Being talked down to with drudgingly obvious and childishly simple messages about racial equality is annoying. It's so, so much better to demonstrate equality by having competent outcomes from a diverse cast.
On the other hand, if quite a few people just prefer to watch the version with a white man, that seems like it would correlate to the shows being cancelled, independently of how entertaining they are..