I guarantee I'm not the only one that stopped posting because I didn't like certain people here. now I haven't actively posted here in maybe a year or two, so I've been out of the loop for a bit. that being said, I think I have a few ideas on why the site isn't as active
1: lack of leagues and/or fun runs. I think back in 2016-17 there was a few different types of leagues and everyone was willing to try out at least one fun run a week
2: some people have limited or are no longer interested in monster trucks, which is what this site is for. I wasn't interested in monster trucks for a while, so I didn't come here that much. then my interest grew again and I came back for a bit
3: some people are simply moving on and aren't looking back. I think I've seen this happen a few times here
4: some people have moved on to BeamNG
5: maybe another reason (though probably not) is because of a lack of content creators? I mean we have some really really skilled guys on here but maybe there isn't enough. take a look at the request form for example, there's people making requests a lot most likely because they don't know how to make the stuff themselves. sure there's guides everywhere but maybe they're too confusing for people or they don't want to give in the effort in case they suck at it
6: the same to what i said at the top, some people left because they didn't like other people or vice versa
there's probably more or other reasons and maybe the 6 I just listed are terrible reasons, guess we'll see