I feel like you're touching a bit on gamer ennui. Stuff might've seemed "new" or the "total package" back then, but the communities have basically broken down into finding the most efficient paths with people just parroting them whether they're actually capable or not. If you want people to care about trash mobs, they need their own value. Maybe it's high EXP. Maybe they drop upgrade components. Pick your poison, really. And while I started MMOing with FFXI, it had it's EQ roots. One could feasibly call HNMs the boss of a dungeon area, of which most people just stealthed past the fodder while fighting for the claim when they did pop. When MPK was possible, people even went to the length to try and wipe rival alliances. If PvP is possible, it's kind of a given what would happen there. Yet, without those things, you risk the game just becoming camping, claiming, and killing with someone or group of someones potentially being left out.
I'm generally against Open World PvP due to griefing, either like the above, highbies ganking lowbies, twinks outmatching the general population, class imbalances, and so on. So, I'd rather not see such as a "solution" and certainly why games like ArchAge aren't getting a second look from me despite their bold promise of a sandbox environment. I hate ******** other players. I hate being screwed by other players. And while some subscribe to the notion that competition fosters community, I can't agree it does within progression games when all things aren't equal.
If you're trying to say the environments themselves should have mechanics, I can't entirely disagree with the notion, but would express concern over how things like lag may play into it. If there's a part of some dungeon where you need to sneak past a guard, otherwise he'd trigger an endless wave of patrols, that period of sneaking would most likely need to be lag free, otherwise you give it a large margin for error that people would just complain is too easy anyway. Things like "You must have this class/ability to pass!" should also be avoided, too. Otherwise, I'd really like to know how you'd fight the ennui because if a location has no worth, not many are going to stop and smell the roses. That's just the nature of people not wanting to waste time, especially if their own is limited.