Also a very important difference between ARK and 7d2D
ARK vanilla you really can't solo unless you are a crazy mofo.
7D2D is designed to be solable (while still encouraging team play). Any end-game content should keep that in mind, and then more than 2% of people would see it by definition. If for ex colonies (I keep bringing this up because this is probably my most wanted end-game feature

), yes it would take some work to build up domination over the world map but even casuals would see at least one or two towns colonized probably, if it is designed such that solo players can accomplish that goal.
My problem with things like equipment being "end game" is that it's, for lack of better words, kind of boring - and really not end-game at least in the sense that I imagine it. OK great I got these legendary weapons... now what? I wanna take on a challenging task now. Liiiiike.... defending my colony and towns from threats even worse to feel like I'm actually doing something meaningful with my new found power rather than just grind for the next legendary weapon just for the sake of grinding new equipment.
How about quests that require you to fend off a town, POI, whatever from a BM-esque horde? Defending a trader? Whatever? There are lots of things that I think wouldn't be awfully hard to code in since the framework is already there. Can even just have stationary NPCs, they don't even need to move. I'd like moving NPC, but can see how they would be harder to code up.
We literally have stationary NPCs now. Why not take advantage of it? I understand the time crunch,
but this is literally already coded in the game already. Quests are also already in the game. As are BM hordes. I don't think it would be too awfully difficult to make some defend quests?