Specifically things like instanced 5 man dungeons (like Ragefire Chasm or the Deadmines in WoW) which are explicitly designed to challenge a full party of a certain level range. Notably, not endgame content. I'm sure the answer changes based on different factors (e.g. how good are the rewards? What are the drop rates like? Are similar rewards available elsewhere? How long is the dungeon? Am I late picking the kids up from soccer practice?), but I'm curious what folks' thoughts are. I'm personally sour on the idea, but I understand that my attitude is "the less MMO an MMORPG can be, the happier I am", so MMO designers should probably disregard my opinion.
Supplementary Context: usually about once a year, I get the bug to hop into an MMO. However, I am not a good MMO player. I tend to flit around my gaming library like an ADHD pixie on cocaine, and there's no telling how long my interest will sustain itself. Therefore, any "meta" choice I make is purely by accident, and I don't spare even a moment of thought on "efficiency". In fact, I've often thought of my dalliances in MMOs as digital tourism. By and large, I'm there to craft, read quest dialogs, and poke around in the weird corners of the map for a couple weeks before logging off for another few years. Anytime I've ever done group content (which is, admittedly, not often), I'm desperately trying to keep up while someone nukes everything in the dungeon as they sprint towards the end. I wind up feeling like my lackadaisical approach is probably fucking up someone else's farming loop. Now, I don't think either the sweatlords or I are playing the game "wrong" so to speak, but our priorities are in conflict. Maybe I'm letting people-pleasing anxiety get the best of me, but I feel like the person that cares enough to grind a dungeon reward as fast as possible should get right of way over my happy ass who will intentionally sandbag my way through a dungeon if the vibes are right. Therefore, I tend not to engage with such content, if it's not possible to solo.
This has all come to a head because my current preoccupation is Star Wars The Old Republic. Given this game's much greater emphasis on story and dialog than a typical MMO, I actually feel like there's RP content that I want to see in the dungeons, irrespective of any item reward. To the game's credit, many of these can be done solo by selecting the "story" difficulty option before loading in, but not all of them. I just don't want to be the asshole holding up the party cause I want to watch the 3 minute into cutscene (or whatever) while everyone else is hammering their skip buttons trying to get to the boss.
Not necessarily asking for advice, as the solution seems obvious to me (it's "talk to your fellow players", like it always is), but I thought this might foster some discussion, especially from old heads who might have lived the raid life back in the day, but now have different priorities.

Deadmines in WoW
Idk when you played but my buddy and I pretty much duo'd the dungeon starting both at level 11. Took down all the bosses except the VC because of the minion respawn mechanic. Had a lot of fun, level 17 by the time we got wiped.
Last time I played, the requirement was level 17 to enter the dungeon. I just laughed. Same with elite areas that got nerfed that I would solo became regular. The amount of runs I did solo to get the barmans shanker lol, that was like the rogues right of passage.
It wasn't fun to see that raids could be 5 manned.
Originally it was like, you need the best fire resist gear so we can clear this raid--forget about all the cool gear you got, that's why I always called dibs on trinkets--proc'ing multiple strikes was fun, I think I did 8-9 once (in other words instead of 1 hit per, lets say second, it was 9). I played a rogue that was a engineer/enchanter (usually engineering goes with mining, but I did it the hard way, buy and sell stuff and farm enchanting mats and sell enchants.
So I would often times rez a priest after a raid wipe with a trinket saving everyone time to run back. It's 40 people, and everyone has only so much time. We all chatted on teamspeak, it was fun to establish a order of communication.
I would say I had a lot of fun playing it when I did; I don't think the modern generation will be able to enjoy something like that.
So hopefully that gets you a better idea of what I think MMOs. Don't get me going on Lineage 2.
Edit: Oh yeah I was tester, so I also got to enjoy the unreported glitches.