People aren't using it because it is no longer receiving updates. 2-3 year old hardware should not be considered "old", or obsolete.
Android hardware ages really poorly. I have an iPad and a few android tablets from around 2014 and the iPad is on the latest version of iOS 14 and feels almost new while the android tablets are basically unusable and on 2015 versions of android.
If the software doesn't get updated, it doesn't mean the hardware is not aging well.
Except for the battery, my GS7 is fine otherwise..
My 4 year old S8 is doing just fine. I'd be happy to replace the battery and use it for another 2+ years, but I only get one more quarterly security update.