This forum did indeed have its "peak" or golden age. Different users would agree on different dates, but in my personal opinion, the best years on this forum were 2009-2015.
In 2014 especially, I'd leave this forum open on my computer all day and frequently refresh the "Unread" tab to see if anything new was posted or if there were any replies in a discussion I was involved in. I had a friend group on here at some point, and I enjoyed posting screenshots or new mod showcases. But there are other games that may be more rewarding to mod, or may have larger and more experienced modding communities, and modders such as myself shifted focus to other hobbies or activities.
The modding community for this game, although they have a special place in my heart, lacked technical experience a lot of the time. Lately, I've been seeing new modders for this game that seem to appear out of nowhere and are capable of making mods that we could only have dreamed of in 2014. But when this forum was more active, the active modders were mostly inexperienced. There was indeed a handful of very skilled modders such as derpy54320(daboss) or MadmaN, but it took about 18 years of this modding community existing before we were even able to print our own custom text on the screen without using the very limited TextPrintStringfunction which only allowed for red text in a specific font. Meanwhile, other modding communities (like Tony Hawk) had mods that pretty much created a whole separate game, just within a few years of the game existing.
Progress in Bully modding has been extremely slow and difficult due to the lack of modders with technical experience. It seems in the last 4 years, there are a lot of people coming into the community with great technical skill that have a lot to offer, but they may quickly move onto another game simply due to how small this community is and how little demand there is for anymore innovation.