The problem with fixating on TERFs is that they do not have political power (in the US at least.) TERFs don’t actively call for trans genocide in the way that conservative evangelical Christians do. It becomes the easy thing of dunking on feminists online.
I’ve also found that people throw the term TERF very freely. Part of that is that bad actors do pretend to be “TERFs” because it lets them be transphobic, without actually engaging with radical feminism. A TERF is trans exclusive because they believe that gender transition reinforces a gender binary. The concerns over “protecting women” can be rhetorically the same, but the motivation is different. There can be some fellow travelers (Posey Parker) - but I think at that point it’s more of a mask off rejection of the feminist part.
I don’t agree with TERFs, and think their ideology can be harmful, but I also think that the obsession with them is a waste of time. Rowling’s books were never good, and it was time to grow up long before she started staying stupid shit online. If people spent half the energy they do bitching about a children’s book author actually advocating for trans rights, maybe we wouldn’t all be intersex by EO.