As someone who has stepped away from Disco multiple times, and now I infrequently surf the forums when I can/want to, the problem is even further than what has been brought up above.
Yes, the group that does complain a lot or say this community sucks, while their opinions have some merit, are probably burnt out themselves. To say that those who are saying the community sucks should make an effort to make it better is sadly not going to hold much sway to the majority of those speaking out in such a way - simply because if you get to the point where you do say the community sucks or what not, the motivation to do anything worthwhile like try to make it better is no longer there. I can speak from experience - I tried to do my part, whether as a staff member or player, but it definitely got to the point for me that it wasn't worth the time and effort to attempt to introduce a change, and it was/is time for me to move on. Sometimes you just are burnt out, and the last thing you want to do is put MORE effort into something that no longer holds the same appeal as it did in years past. Nothing wrong with that either.
I'd say instead of calling out to those saying the community sucks to make a difference, it needs to come from those who still find value in their efforts here. The ones who are willing to put forth the effort of trying to make it better. Many will fail, many won't see their efforts come to fruition, but some will get through. Some will be able to hopefully and ideally make an impression/lasting change. Again though, you need to find the people who aren't jaded or burnt out. Those are the last people you should try to appeal to.