@Eddie DavidsonI used to frequent this particular forum quite a while ago, and it has some very good ideas. I'm not sure what happened between then and now, but I haven't seen many 'usable' themes for some time. I never used any for a story premise of my own, but I did aspects of some in my ongoing stories.
As for the more judgmental responses, those mostly come when someone requests more Pedo stories, which are expressly forbidden both by the site and by Canadian law, and could get the entire site shut down. Thus, to help preserve the site, many will attempt to sidetrack those efforts before they progress very far.
However, there are other ideas which just haven't been well enough thought through and developed to actually make for a sustainable story. I've seen several of those arguments here, and the reasons are generally well defended, IMHO.
The bad puns, however, are mostly an attempt by certain individuals (myself included) to help deescalate rising tensions in the discussions, especially when two or more authors face off in little more than a shouter match, insulting and belittling each other. And once the pun-wars start, they too escalate rapidly. For the many authors who routinely 'punish' their characters for the sake of story conflict purposes, it's nice to let off some steam by playing on other author's often poor phrasing choices.
By the way, I've also offered a couple of ideas here for story plots which I discovered I couldn't follow through on. However, those nary got a nibble, and nowadays, I more often get near the end of a complete first draft before abandoning a story, and at that idea it's no longer an 'idea' but a fully fleshed out story.
The bigger issue, as you've apparently noted, is that each author has their particular shtick, where it's harems, incest, revenge fantasies, or whatever. So, it becomes difficult to find suggestions that match your particular impulses and desires. It's one thing to put a slightly different spin on a common story, it's another to change the central theme entirely to wrap it around a different premise.