I can only speak for myself but once I finished my goals in a piece of content, I will focus more of the limited playtime I have a day on my unfinished objectives.
Naturally I go back to „completed“ content here and there, but not as frequend like I did if I was still chasing something.

As for lack of future proofing I disagree to some level. I did the Dalradia instance with 3 people once, since you get insane buffs in those if only a few people join.
Not a perfect solution, but at least something.