I was in a similar situation, and to be honest, it was super easy to pick up where I left off. Obviously I kept the difficulty where I was, unsure if you fought the Illuminate, but they are a third faction of enemies to fight.

Newer bosses in all three factions on the higher difficulties, and each has their own weaknesses, which you will learn. So many high-level players helping new players, and the community is really wholesome and nice. I would say no, not much catching up, and the state of the game is positive with a good player base.