There could be a lot of small reasons for the decline of this forum but I don’t think there is one definitive one.
Could be a demographic shift in users. Our new crop of young employees are somewhat less curious in creating new scripts for themselves. There is definitely the expectation of things just working out of the box. There is also more automation in software now then there was before, so maybe interest in solving problems programatically is less ingrained than when almost everything needed to be “programmed” (I use this term loosely, anything that is not GUI is considered programming by most not familiar with some form of coding ). Even explaining simple batch/cmd scripts is met with blank stares.
Tighter deadlines, less room for exploration. Fewer companies are willing to invest into scripting in general as availability of plugins to do the work or get close to the desired result are abundant. General trend of the disappearing middle, there are less middle sized companies and more small companies operating on the edge and large companies with enough resources/expertise to develop entirely in-house (proprietary script/production pipelines are closely guarded). We don’t have a dedicated scripter/developer/programmer, I started doing it purely out of necessity to meet deadlines.
Mixture of extremely experienced users and inexperienced users creates friction, new would-be users leave for different sources. Questions asked are either of really high difficulty or really simple (answerable by maxscript reference). Mid-level users feel intimidated to answer question, even though they have greater ability to empathize with new users and explain issues in less technical accessible terms. This is endemic of general programming community.
I can only speak for myself.
This forum is my second go to resource for maxscript next to the official maxscript help. I barely have enough knowledge of maxscirpt to pose a question let alone answer them, I certainly don’t want to lead someone down the wrong path. I try to answer when I can but mostly the day to day works keeps me pretty busy.