If we're going to be philosophical, I'd say that to me the core of feminism is (a) centering the needs of women and girls and (b) asserting that women are equal to men.
Beyond that, there's an almost infinite number of ways to be feminist. It doesn't require you to sign up to a laundry list of policy positions on net zero or Ukraine or the marginal tax rate or whatever.
I say almost infinite, because I can't see that the belief that men can be women is compatible with feminism, and the feminists I've seen up close who take that position invariably devolve into centering the most special oppressed women of all i.e. the male ones.
However.
We do get trollish derailing, but IME lots of the scraps here are not derailing as such, they derive from us bringing different perspectives, and sometimes there's a bad tempered interaction where it might have been profitable to dig into why we have different perspectives.
The obvious one for me is that, while FWR has traditionally skewed left, many of us feel politically homeless. But there are some, a minority I think, for whom it's very very important that feminism has to be left wing, and you can't be GC unless you're also explicitly left wing. This often comes with an assumption that if you're not explicitly left wing you must be right wing; a side order of sneering about "GB News" or "Tommy Robinson supporters"; and an assumption that being left wing means you're morally superior.
The last is a particular berserk button of mine, precisely because of my up close experience of dodgy left wing men, and the left wing women who enable them. I can speak at tedious length about this if needed.
Rationally it would be better to ask "why do you think that?", but if I'm tired or ill or irritable and someone is yapping at me in an annoying way, I may not do so.
But that's not really derailing. That's just human people arguing.
We can spot derailing when we see it, which doesn't make it less annoying.