I can go back to any of the content you're talking about and re-do it at my own pace. I never relied on what I got from that content to 'boost me ahead of the crowd' that didn't do it. PotD/HoH got me levels and some near glamour items/mounts. The rewards didn't do anything besides let me show off a little bit.

Eureka was way too confined to its self, so you couldn't do anything else while working on the grind, which did push a ton of players away from it, as well as bringing back archaic game designs like leveling down if you died. No way to continue anything related to your relic in 4.X outside of Eureka. It was all or nothing. It tried way too hard to be FFXI 2.0 and I stopped going there when I got my one relic that didn't have an elemental bonus on it because that would require me to join way too many people to finalize my relic.

Bozja was partially tied to the relic, partially tied to some side story content, it was the 5.X version of PotD/HoH in a way that you could level up from level 71 to 80 in there which made multi taking VERY NICE FOR MANY PEOPLE, and a few other things I don't remember off the top of my head. You could work on the relic while outside of Bozja, which I made ample use of working on six relics when I didn't want to deal with other people for a bit. There were glamours, mounts, and other things you could only get in there but again it was optional to go after them, and many things could be sold on the market board so others could buy them from you. The relic is only a tiny bit better than the savage weapon, since you could change the smallest bit of stats on them


The worst of the content you're saying is 'parasistic' honestly was Eureka. It catered to only a certain percentage of the population, and it only got 'better' in the later stages of it, but some of the stuff you still couldn't do without getting a lot of people for it. All the issues they had there they fixed with Bozja, still has issues. But there are some groups of players out there that have discords for that kind of content.

There's groups for almost all kinds of content, including people I see advertising discord groups that focus on PvP during weekends so people can still play it.

But none of that will make/break you for anything that isn't related to it, compared to the crapshoot of systems I have heard that WoW has.