I have roughly 20k hours in Oldschool RuneScape, and around 5000 in modern RuneScape. This would be a very long discussion if I went into every aspect, but I’ll keep it short.
Oldschool RuneScape has a very community focused development process, where what the player says, goes, for the most part. Couple that with the sense of progression and the depth to the mechanics of combat, although at first glance it seems simple, it is one of the most rewarding games you can play. I highly recommend giving it a shot.
While the modern version can still be fun, it is hindered by not being as community driven, having 20+ years of jank built on top of jank, and heavy monetisation (although this is being addressed), just makes the game fall very short of its counterpart for me. While the combat has quite a lot of depth, it doesn’t spark that sense of progression or achievement.
Np, feel free to dm me if you pick the game up and want some pointers!