I live by a park where there are 3 Pokestops and a Gym and it used to be mildly crowded, now it's empty. It's obvious that the game has died down and it all can be traced back to when Niantic broke the tracking system and proceeded to go after Maps.
Every "anti-cheat" measure they introduced (Detecting movement speed and root) netted a large number of false positives and they refuse to listen to their active and vocal community.
Not to mention the inherently broken Gym battle system where anyone can take over a Gym even if you were the one to beat the Gym owners. That was the one aspect I found too frustrating.