So what exactly you could do in Tanaan that was better than Legion?
Farm apexis, savage claws - same stuff, we just have different currencies.
Farm reps - same stuff, plus WOD reps were pinnacle of boredom, and now we have paragon reps.
Camp doomroller for 1% chance for mount - we still have rare drop chance mounts to farm.
Do fill the bar dailies - we have now WQ, same thing, just more of them.
Farm rares for baleful tokens - we have rares on broken shore and dauntless tokens.
Farm achievements - we have them now too.
Do pet battle dailies - we have them now as well.
World boss - we have more of them now.
So what exactly Tanaan had that people praise it now?
Is it that time of the year already "remember WOD, that was a cool expansion"? I thought people claimed WOD was the worst thing to happen to WOW?
Most MMOs are either grind shit and gank people or spam dungeons / raids / scenarios (or similar type of group content). Some have more organized pvp and concentrate on that.
Challenging open world content is an oxymoron, world content is always either a mass zerg (like Guild Wars 2 world bosses / events) or a griefing fiesta if the MMO has open world pvp.