Going from single player to multiplayer is like going from the pond into the ocean. The real action happens in the ocean, but it is not for the timid. I look at single player as just a tutorial for multiplayer.
Possibly. I don't really want to play against people who have been playing competitively for 16 years. And I like messing around in single player, building cool bases or trying different strategies. Not trying to be as efficient as possible and micromanaging every single unit. Competitive multiplayer games in general have never really been that enjoyable to me.
Ok I went back and tried another game just to see if my first impressions were entirely wrong. This time there were a lot of noob maps and some less skilled players to play against.
I joined a 4v4 map, and while I still didn't do great, I had other players to back me up. I also didn't feel like I was the worst player in the game.
However just as the game was getting interesting (and I was probably about to get crushed), everyone paused the game and kicked me. Possibly because they blamed more for their lag, possibly because I wasn't that good of a player. They didn't say. It was very discouraging.
But it wasn't as bad as I expected it to be, and I might try playing again some time.
Battle for Middle Earth did that quite well. You could play on a ladder system that paired you up against people with a similar win/loss ratio. A friend and I used to play 2v2 quite a lot. We got to the point where we could comfortably beat 6 AIs and we were OK against people with a little online experience. Occasionally we played against serious people from the forums and got thoroughly destroyed.
It was fun, but beyond casual battles it became too much like exploitation of the engine - e.g. having to destroy farms yourself because you didn't want to give the enemy units experience.