A lot of us oldies have gotten really busy IRL with jobs, house moves, weddings, travelling etc. I became more active again a few years ago when I had time off before the start of my PhD, and during my 1st year when the workload was a bit more relaxed. But now, in my final year, after the long lab hours and all the reading and writing for my thesis, I just don't have the bandwidth left to write or review much of anything outside of that. There are the occasional bouts of inspiration to ramble about my recent fiction reading, but nothing like when I was writing for the MR Canon... and it is doubly hard to be motivated to do so with the general reduction in activity and engagement with posts.
Unfortunately, forums are not really the fashion anymore, although MR isn't terrible to use on a phone/tablet. I should probably make more of an effort to engage in the Discord myself... unless something weird happens in the world of the internet, I imagine that's where an MR revival could actually happen, as it can facilitate group calls with screen sharing, instant messaging with notifications, chatbots with all sorts of functions, easier image uploads etc. The only thing that it's not as good for is acting as a direct repository of work, but linking to personal cloud folders isn't so bad.