There are new monsters in swamp and plains, and a new dungeon in the mountains. A couple light armor sets and a few new build pieces have been added. Food has been completely reworked, along with blocking which now is paired with your health. Up to you if you think that's enough to jump back in.

One reason why people still play is because no other game has quite the same feel as Valheim and the procedural maps make every playthrough different. So the people who like to play challenge runs (permadeath, no portals, etc.) and build stuff are still around.