What everyone else said.
I never played D1, but this launch reminds me a lot of The Division at launch (which of course kind of copied Destiny) (minus the additional Dark Zone grief fest of that end-game). Both are fairly enjoyable casual romps through interesting spaces when playing with friends. Single player, the campaign is sub-par at best. The setting/universe is potentially great but the actual story-telling is plain bad. And once you hit the level cap, which doesn't take long (if you disregard the 299->300 deadlock you'll likely end up in), there is nothing left to do. Same near-zero interaction with others as Division, too.
I never went back to the Division, though I hear it's improved a lot now. D2 is probably going to end up the same. I'll probably grab Osiris because my friends are, but I can't see how they'll be able to make changes that are substantial enough to keep me around or want to return for the next one. Based on the feature overview, it's mostly more of the same stuff with an extra location. And some kind of Diablo rift-like dungeoneering. This doesn't work at all without some actual loot incentive. Right now, it's a loot treadmill without the loot. Power/light is just a number and feels meaningless. You'll reach the soft-cap on your first character in a matter of two weeks right now, and that number is time-gated. Meaning that after you hit 20, you can finish all the weekly stuff that you can get progression from in a single evening (3-4 hours). Add another couple of hours for the weekly raid. The mod system seems like it was made to be annoying when trying to do what little build customization the game provides, by destroying your currently equipped mods when swapping. And the whole mod system is based on gambling rather than just getting to buy the mod you need. Add "YOUR INVENTORY IS FULL" to this. Gaah. Gear level is just a number and doesn't seem to matter at all so long as you're above the required minimum for a specific piece of content. Some guy on YouTube tested the same scout rifle level 100 vs 250 on some mobs in a public event. Same exact damage numbers.
Ah yes, the inventory system in the game is downright atrocious.. Just wtf.. How these game studios manage to build these incredible engines but fail so miserable at simple UI stuff will never cease to baffle me. The game would be unplayable without DestinyItemManager. Kudos for providing the API to let the community build tools like that, at least. But they can't fix everything. Why do shaders and emblems have to occupy inventory slots? Why can't emotes just be shared across characters (oh right, microtransactions)? Why do "quests" like rat-king take up inventory space?
Besides the core gameplay, this game feels half-finished in so many ways.