It's not just this hobby that moved away from forums in the mid-2010s. Much like anything that becomes successful and makes a few bucks at the grassroots level, the money people step in and think they can do better. Many forums, both big and small, were acquired by two forum aggregators. Some went for big bucks, like 7 figures. To pay for these purchases, advertising on forums grew exponentially. As the owner of a site and part of a team that wrote plugins for forums, we witnessed the shift when our former small forum owners let us know they had sold to one of the big two. Our own little forum plugin company and my site were bought out for stupid money. I did some consulting and Q/A work for them, then bailed when the corp BS got too much for me. Been semi-retired ever since
Thankfully, Art was not dismayed by all the machinations and created ScapeCrunch. Become a member, support the independent. It's less costly than a box of aquascaping rocks, and more informative too.