Such questions are, strictly speaking, XY problems
The question of a site’s “legality,” strictly speaking, is
unanswerable: It only becomes known after a court ruling. And strictly, that ruling only applies to what the site was doing at the time it was sued, not to anything they’ve done since.
useless: These matters almost never actually go to court, so the undecided question of “legality” won’t ever truly be decided. Therefore it won’t affect anything, including the querent, the site, or the copyright holder.
But people asking this question aren’t literally asking “what is the court ruling on this site’s use of this material?” which is, strictly speaking, what “is this site legal?” has to mean. What they want to know is if there is something immoral and/or dangerous about the site in question. They want to know if using it is damaging the publisher they want to support, or if the site is going to disappear on them, or if they can get in trouble for using it.
And those questions are things that we are best-suited to answer. We know the landscape, copyright holders, the things that are acceptable and unacceptable. We can and should answer those questions.
“Teach a man to fish” is not an acceptable answer, in my opinion. Because the actual answer isn’t something we look up, or reading licenses, or whatever. It’s experience—knowing what kinds of things, historically, have been considered acceptable by the copyright holder, and which things have not. What they have said is acceptable. And so on. We can’t transfer that knowledge and experience in an answer. I don’t see any way to actually accomplish this in a useful way.
Instead, we should put a banner on it disclaiming legal authority and pointing out that “legality” barely even comes into it, and then answer the question. And if the question links to the site that’s being questioned—and this is a sincere, genuine question, not a “subtle” attempt to promote a piracy site or whatever—the link should be fine. Maybe if it turns out to be a piracy site, we edit the link out and just describe the site by title or whatever. But even if we leave the link in, the only real danger there is link rot—which, if the site dies, the entire question is completely historical anyway so it doesn’t really matter. Such a question is unlikely to cause any other troubles for the site.