You already know all of what I'm going to say: one of the reasons is because participation rate is usually extremely low unless it involves drama.
There is only so much one can do before it looks like just one person is discussing the topic. If no one replies? Too bad, I don't want to have 10 comments in a row belonging to me, I'm not that nutty.
The other problem is a lot of the active members can't resist replying to troll posts, I've had to actively suppress that itch myself.
Someone says something dumb? A bunch of easy replies roll in, reactions are given out, dopamine fix obtained. Now off to find the next dumb statement to reply to.
And I said "active members", I'm quite certain there are a decent number of lurkers who don't post or reply much, either because they aren't compelled to, or because a lot of the dumb drama discourages them from participating to begin with. Or maybe they're just too busy enjoying their games
Old threads are contextual, in some cases I post there when it fits, I've seen one or two that I didn't post in get closed for necrobumping or it just gets pushed out of sight by the typical drama threads. Heck, if you post in an old thread and it gets noticed, oftentimes the first three replies will be variations or gifs of "Damn, that necro" (aka low effort replies).
As for this thread? It's just the result of the Off-Topic Resetera thread being closed and someone wanting to stir up easy drama.
I will say the recent update that would suggest related threads at the bottom is a great addition; it's how I came across your Vice Danmaku thread.
These are my 2 cents and I'm still using the great bit of wisdom you imparted back then: "Don't take it too seriously, it's just a forum". Cheers man.