Do you know how you can tell a game is still getting new blood? Mid-level group quests full of people that have never done them before. Early level might indicate free trial folks, and many people have not done everything at fifty, but The Lord of the Rings Online™: Shadows of Angmar™ epic books are something I expect every veteran to have done at least once.
Do you know why you level faster solo? Your time is worth nothing to your teammates. They are quite happy to make you wait for them, to go in some random direction rather than following a lead, and to ignore instructions from people who have done the quest before. If someone is two steps later than you on a quest, he has probably just done those steps, so you should listen to him if he says to run a town over then come back. No, you won’t just wait there for him, run to the next town to talk to whoever or else you will be stuck a step behind on the quest chain.
Do you even know how to read the quest instructions? It says to talk to someone in the next town over. You cannot catch up with us if you will not follow the quest instructions or the repeat of them from your teammates.
If you have a partner or a group on which you can rely, you can level faster teamed than solo. A nice thing about being in a guild is that even if half of them are idiots, you know who the idiots are.