Yopop, once you hit lvl 90s, the game is just starting. There are missions to complete, high level quests, and most of all, gears to collect. That is just the tip of the iceberg. With recent news of tweaking the older contents, there will be more stuff to do still. The upside is that at lvl 90s, things are more doable with less people. As for people being clueless, do not blame them, the game is NOT very informative at all, and the only way you can get info is by googling or go to wiki. No help is given in the game itself. You are not learning your job by having a 6 people party from 1-75. You will however learn your job A LOT by solo, duo, or trio. In fact, 1-3 people party forced you to really learn your job since there is no safety net and everyone has to pull double duty and work as a team or face wiped.
As for xp gained, Abyssea is the hands down best for xp per hour, though sometimes you do need to take a break, and it's nice to know that now you have a lot of options. By making the game much more doable with less people, it makes it more intimate, fun and less of a time sink. You get to know the 3-4 people that you do seals farming a lot, and everyone actually get something in return. The game is better than ever now simply because you have options and a lot of things to do once you reach lvl 90.