A couple of things, in my opinion.
1.) The weapons aren't exciting. Gjallarhorn was overpowered without a doubt, but it was an exciting weapon to get and use. I think the weapons, and loot in general, seem kind of stale. The weapon handling is still really solid, I just think design wise they aren't really interesting for the most part. I don't find most exotics all that interesting either.
2.) There's really nothing to chase after once the player "gets" something. SInce RNG rolls don't exist and there's really nothing else to substitute for it, there's really not a whole lot to chase after unless you really like a certain gun that you don't already have, there's really not much to get. Even with the events that they have had, I don't think they've really added anything substantial to the game.
For better or worse, that depends on the player of course. Personally, I think it's still a fun game but I feel like Bungie went too far away from the RPG stuff in their game that I think it feels like it doesn't actually serve much of a purpose. It might be better than vanilla Destiny 1, but I don't think it's anywhere near as good as post-TTK Destiny 1.