I don't think the type of threads allowed is a problem. If you don't like it, don't read it. I've only encountered this as being a rare problem on forums if one type of thread gets spammed over and over again. In fact, this forum seems to have the most strictest mod action regarding locking threads that I've seen on any forum: Mod doesn't personally like the thread topic? Let's lock it! Disagree with the points being made? Let's lock it! A few posters causing trouble and we can't be bothered to deal with it? Let's lock it!
So I don't think being too lax in locking threads is the problem.
One problem is that not everyone agrees with what counts as a worthwhile topic - so you might rather not see those sorts of threads, but other people might. There are lots of threads I don't like, but I don't see those getting locked.
This is off-topic, after all, so why are some things off-topic? Perhaps there could be more sub-forums to that politics etc didn't get put alongside any random off-topic thread.
On top of that I think they should try to ban certain topics or close popular threads if someone (or certain posters) doesn't behave. So the people who were seriously debating the topic will be mad at the people responsable for the ban or the closure. Much more effective then warnings. It works on other fora.
No it isn't, and no it doesn't - that just makes me mad at the mods. And the troublesome people don't change their behavior, because they are not dealt with. Even if people are mad at them, why should they care?
I speak as someone who is a mod on another forum. We do our best to deal with individuals rather than just locking all the threads. If you do that, why bother having a forum? A forum you can't post to must be 100% flame free, so it must be good!
This is the same sort of logic teachers give in school when they keep the whole class behind, saying the other kids should have stopped them. Which is absurd, because they don't have any powers to deal with it, unlike the teachers.
Since regular posters are unable to have the powers to deal with troublesome posters, it is equally absurd to cause them to get mad at the troublemakers. If I see trouble stirring up again, what am I to do? I'm less likely to report it to a mod, if they just lock the thread again. Perhaps I'll tell him to STFU, but that'll just cause the flaming to get worse.