My Galaxy S7 is 4 years old. It's still very fast (never had to reset it) and still gets security updates (last one in August) although no more OS updates.
If I played AAA games on my smartphone, I might want an upgrade, but I do my gaming on PCs. Otherwise newer models don't really have that much appeal, except for the better camera (although I am not impressed by the fake bokeh effect). However, even for the camera, it always feels like a compromise whenever I use it, in that I put up with lower quality in exchange for convenience.
What's not to like?
My last Android (Nexus 5) stopped receiving updates just 2 years after I bought it, because of some ridiculous graphics driver bs.