I believe you are correct that the volume of topics of general interest in this section has declined significantly. I do not believe that the subsections are the reason for this drop, because many of them are not very busy either.

I have noticed several trends, however:

Attempts at serious discussion that are not directed toward promoting mirrorless technology are routinely attacked and denigrated by a fairly small but very predictable group of bullies and detractors.

Attempts at serious discussion that are not directed toward saving raw files and doing extensive post processing are routinely attacked and denigrated by a fairly small but very predictable group of bullies and detractors.

A number of knowledgeable and helpful posters have either ceased posting altogether or have significantly reduced their contributions.

Although the vast majority of members are certainly continuing to pursue their interest in photography with mirror box camera equipment, those in this group (including me) have demonstrated, and continue to demonstrate, that we do not feel that we have a viable platform to discuss those questions, issues, and problems here. I have a list of topics that I would like to initiate, but they will never see the light of day here, simply because I do not have any interest in dealing with the trolls and detractors. I have other venues where I am discussing those topics quite productively and without anywhere near the indigestion and heartburn that would arise here.

In short...I believe that you are observing the slow death of this forum due to the bad behavior of the participants.