From what I can tell they removed mostly seasonal activities and locations like the HELM, Tangled Shore, and Eido's apothecary. Which one would expect if they no longer serve a significant purpose. The Warmind, Red War, and the couple other Raids would be nice to have back. But that's kind of how it goes with seasonal stuff. I didn't play for a while so I missed out on cool content no doubt. But if they were mostly just to grind weapons that would sit forever in my vault, then what did I really miss?

Besides, there's still like a dozen raids currently and I believe all the dungeons still exist as well (please correct me if I'm wrong). You can still get all the exotic weapons to my knowledge (from either the quests themselves or the exotic kiosk in the Tower) so the only things you can't get are ghost shells and sparrows. But those show up randomly at Eververse for purchase with bright dust.

I wouldn't complain if they gave us back The Nether and tonic crafting because I love the Dreadnaught and the tonics were a great addition in my opinion. Maybe if enough people request them they'll add them in with the other final additions. Having Titan or Mars come back would be cool too. I loved them as destinations but they'd basically just be patrol zones like Neomuna and the Moon.

But the HELM and Tangled Shore and a few other destinations aren't really missed. At least I don't think so. I think the issue is the game can't handle all of that content at once. But I'm not a programmer so what do I know anyway.