Sounds like the left when they want to cancel right wingers.
Grind it out, be more entertaining or say hey, you know what, I am not keeping it alive, they are.
If they are not toxic, their rate of posting is their freedom and keeping a dead site's subforum from the brink of stagnation into a coma.
I'd take a shitposter with passion over a lurker with moany vibes any day.
That said, in the religion forums BrotherD and some other did make it so their actual harassment, not just spamming, drove sensible posters away and I am glad that got handled.
Someone's shitpost is another's wisdom or comedy gold. I firmly believe it. It is a bit like a BDSM crowd wherr you are repulsed by their kink and want to ruin their safe space so it becomes more palatable to your kinks vs limits.
Learn to coexist. Yes, that is coming from me. Despite what everyone says about me, I was never a fan of censorship on anything other than bullying or harmful encouragement to genuinely hate a demographic to serious levels.