RoS is pretty fun, dont listen to these people who spend 150 hours playing the d3 ladder reset and complaining about how game is dead, but still lurk the forum.
There is no trading, however if you need DH gear and run in a party of 3 other DHs then you all are getting DH gear and when you find an item in a party, you can give the item to anyone else who was in game with you for a limited amount of time (several hours). This is the "trading" for D3 currently (looks like it wont be changing).
If you're enjoying the game, dont let people on a forum tell you that you shouldn't be having fun...
The never ending quest of the game is basically complete season journey achievements / higher Grifts / Complete fun and wonky character builds to enjoy the game with
Play through the story mode if you haven't in a while, it's fun. If you just got RoS, play through the new act (a5)
Power leveling still exists, check out communities. There is a community for anything you can think of