For me, I sometimes take priority seating if it's right in front of me and it's crowded on the train. No point keeping it empty and wasting the seat so to say. Bit you'll need to keep an eye out foot those who deserve the seat more.

Speaking from personal experience, that wasn't the first time I encountered a priority seat gatekeeper aunty. I got scolded by one myself before, and I admit my fault as I was too focused on my phone at that moment and I didn't notice the aunties coming in.

I took the seat because the coach was super empty on that Saturday morning when I boarded it. The aunty who scolded me proceeded to sit on two seats, presumably not to let me take the seat.

I almost never took a priority seat ever since. Not even when my feet was injured(it's not visible).

priority seat policing is to me, a heavy responsibility, and I don't find most self-appointed gatekeepers necessarily the most sensitive souls around. I think they play an important function because part of what makes society function well is norms-policing. But are opportunists such a big problem such aunties must exist? maybe! but... invisible disability and injuries are just as good reasons to take such seats, but such aunties make such a bit deal over norm-breakers because social shame is a big reason why their schtick works. But let's say it's someone who's pregnant, not showing, and is having the worse case of vertigo? it goes back to what I started with - most of these aunties aren't into this to take care of people, but to yield some small amount of authority. because in that hypothetical such an aunty should be able to gently assess the situation (ideally?) and more importantly, just as loudly apologize if they get things wrong. And that, I never see.

TLDR, sure I find there's value in those gatekeepers, but those gatekeepers better know what they're doing, since god has seen fit to give them the sort of personality that making a big noise in public isn't a problem for them.

ETA: in a POV that sees them as a good addition to society, I actually agree that they should keep priority seats empty even at peak hours. you don't know when an emergency will happen. but all the above (on the responsibility of it all) comes first.