If I may be really harsh and honest for a bit...
I just lost interest in the tone of conversations here on this forum. COT seemed to take over the forum volume shortly before the re-launch and I generally don't recall paying much attention to COT except for maybe checking in on 'Whats On Your Mind' with other user's life events that I still remember. There were many posters who just posted shit. Useless posts. I don't even remember if I was a mod at the time but I feel like we should have banned shitty posters far more often. And I don't mean my problem was with everyone's overall post quality, the problem was with the users who dragged down everyone else.
I progressively moved to posting on Facepunch since I was also a member there since 2005. And they were notorious for brutal moderation, which in hind-sight helped a lot. You weren't banned for having a different opinion. But you'd be banned for putting in no effort into a post, just posting a meme as a reply, or just throwing out something which didn't add anything to the conversation. It helped shape the quality of posting over time. But I think it only was able to work because that began when the forum was incredibly popular. That won't work now. Maybe if you began doing hard culling in 2012 when it was still a solid active userbase. But now it doesn't make sense to ban for community control. You don't have that kind of margins anymore. Essentially, I think lack of pruning drove away lots of long time members.
It also had a much more vibrant community in all sorts of ways, with much healthier subtopics. Granted, it was rooted in a few games like GMOD and Rust which of course brought in most of the initial users but it grew far more to rely on its community than game discussions and wasn't *about* those games for many years. When Garry killed it a while ago the community made a replacement which is now doing extremely well because the structure, format, and moderation expectations were well respected. It's called Knockout. Bit of a riff on the original naming.
But that said, this forum while a huge part of my life for a long time. And obviously Halo, in all senses, was the core of the community. In my eyes, Off-Topic was supplemental to the core though. Not *why* a user would want to join. When I drifted away from Halo as something I actively played and cared about, the non-Halo discussions didn't keep me here because well most of what I saw and see is low effort. I later got more active on Reddit where you can find any number of unique niche communities and I had my fix for better conversation and there you go. You create your own slice of internet discussions as you see fit. Servers, PC hardware discussions, games criticism, video editing, esports industry, etc. Why come here again at all?
Add that to Discord becoming a competitive 'Other' social network with its own independent communities, there are so many more fixes for socializing than forums. Specifically message boards. They struggle these days I think. I have my own small Discord for my stream. I help manage one Elgato Gaming. And I'm apart of a few Youtuber friends ones which keep me busy.
Recently, I thought about this forum again due to the montage collection being shared around once more and also Halo CE relaunching on PC through the MCC brought back many memories of posting Halo 1 PC videos in the subforum, learning video editing for the first time which ended up leading to an eventual career, and making friendships which shaped my life in various ways.
At the end of the day, I have very little reason to come here as an almost 15 year poster because the people I did post with back then I know on Facebook (Cursed Lemon, Slater ohm, Hable, TM22, Fragtality, etc) or I literally work with in the case of Steggy. Generally just to check in with how I'm doing. However, as others noted, it's still a nostalgia draw. I wish I had more screenshots and videos saved of the forum experience itself.
I'm glad the forum is still around and I'll continue to pop my head in. But I'm turning 30 years old soon, I don't feel like it's worth it to read a forum that sounds like it did when the userbase was 15. I wouldn't even want to read posts from my 15year old self either. Which reminds me of the time I posted a terrible montage, got mad at anyone who said it was bad, and then deleted all my posts only to come back a year later.