Honestly, I have very little issue with D2's end game. But, I think there could be a middle ground between what they have now, and what they had going in D1, which was more of a long term loot/mats grind.
I never got heavy into D1's grind, and I think D2 does a far better job of keeping you hooked by giving you the constant dopamine hit with the endless flood of engrams.
The problem comes once you hit 265-270 and 95% of engrams you get are suddenly useless. Weekly milestones are all well and good, but you can grind through those an evening or two.
It would be really nice if they added some grinds that took a lot longer and rewarded you with the most high fashion items and shaders in the game. Or if they generally varied the amount of time you have to grind for certain rewards.
So let's take uh.. Gunsmith engrams for example. You can get one of those every fucking half hour. I realise that's because you end up dismantling all your loot from ALL your engrams, but bear with me, just for example's sake. So, since gunsmith engrams are easy to get, I don't have an issue with them no longer giving me anything useful past a certain point.
Contrast that with say.. Crucible or Strike engrams. They take a fair bit longer to get. That's fine, but give me a set that I can't get anywhere else for my trouble, and maybe use how long it takes to get an engram for that vendor as a reference point for the power level of the engram.
Anyway, granted, I'm not as hardcore a Destiny player as a lot of people, but I found the game so disgustingly, ruthlessly compelling and addictive for the first... Hm, 2 weeks, that it's basically all I did with my life. And then it became all about weekly milestones. Now I've basically stopped playing altogether. I think what could rope back in is some grinds that would take longer. Give me something to WORK towards now that I've exhausted the easy, quick loot grind.
Either way, I think they've taken very positive steps forward with Destiny 2 in many regards.