You are right about one thing: World of Warcraft has to be played with other people. After all, it is an MMORPG. Not only that, though, I think you need to know who you are playing with IRL too.
When it comes to the pace of the game, if you know what you're doing, it actually is pretty fast. Also, there isn't any grind. The experience is very quest-oriented, so you always feel like you're getting something done. You don't just run around a map and smack things for hours. If you are trying to level like that, the pace is obscenely slow. Since World of Warcraft is so story-based, if you aren't questing, the game pretty much punishes you for it. The monsters don't give you that great of EXP compared to quests. You can easily get to Level 10 in about two hours or so. That's pretty much a single session--at least for me. After that, if you keep questing, you'll keep a good leveling pace. The problem is that if you don't use things like the auction house and professions effectively, you're going to struggle a lot.
Besides, World of Warcraft is a pretty expansive game. No one is forcing you to go fast or go slow. You don't even really need to level very much to be successful. There's events always going on, you can work on your various professions, or PvP. I'm not much of a PvPer, though.
Honestly, I wasn't a fan of World of Warcraft, either. That was way back in the day, when I was just playing it by myself, though. I wasn't really sure where to go or what to do. Without someone there to explain the basics of the game and help me out with the more advanced game mechanics, anyone would have a rough time. Luckily, I did have help this time.