I'm in a guild, and I raid with my guild when I can make the raid times.
Okay, complete disclosure here -- I loved how easy it was to gear up by the end of Battle for Azeroth.
For many players, the first thing they do is survey the mismatched set of greens and blues and that one legendary they didn't manage to replace even though it stopped working around 116.
Blizzard has been tweaking dungeon difficulty and ilevel drops as the expansion progresses, and PTR datamining from Wowhead have shows more gear and difficulty changes for Normal, Heroic, and Mythic dungeons in patch 7.3.
So you want to start raiding Tomb of Sargeras, but you don't have enough gear.
Unless I'm rolling with friends, people I know, I've gotten to the point where I simply can't group with other players.
It wasn't until Timewalking's debut that I really started to appreciate Eck's presence as a bonus boss in Gundrak.
I run one or two dungeons a day. I used to run more, but once my gear got better than anything in them, it wasn't really worth the effort beyond the dose of garrison resources, and now I'm mostly running that second one out of pure stubbornness.
Sure, the challenge of heroics can be fun — and challenge modes, in particular, are a great way to push your abilities. But running heroic dungeons for gear? It's very hard to recommend.