I've also noted that things have been slowing down.
ACS's barrier to entry has definitely contributed to this - reddit and hopup, even facebook have much easier access to classifieds. Not saying I think it's a good idea to remove the system ACS has, but it might be time to open a discussion about it.
I guess the best question to ask is what does ACS bring the the airsoft community?
It has always had the classifieds - and the safest ones at that. But it's other features have been on a sharp decline.
I see very limited tech information posted, in both people asking questions and people answering them. Tech Tuesday on reddit has been dominating that market pretty heavily.
Game days and club schedules have moved to bigger social media platforms such as facebook and discord. It used to be that every group had a post on ACS with information on their group as to were to contact them and what they were all about (here's mine for reference
https://airsoftcanada.com/showthread.php?t=182563).
Gun reviews have moved mostly to youtube. Proper longform typed out reviews are very uncommon and haven't been seen here for the better part of 5 years. (just as an FYI longform is way better then the "look at my shiney AEG" reviews then we get now)
To sum it up, their just isn't as much relevant content here as there once was. If we want to revitalize the form, we need to improve the content.