Steepster has been pretty dead for a few years. I would check it once in awhile up to a year or so ago, less this year, and there were still people lurking around, but minimal discussion activity. It's hard to say how many people were still using it for reviews; maybe a good number, or maybe not many.
All the groups or sites seem to experience a life-cycle and later decline. More activity has centered on Instagram and meetup or interview variations for awhile, than any form of group or forum. The one Discord server is active and that's about it, and it probably helps to be in your early 20s to feel like that's a good social theme fit.