As far as the learning curve goes, I can't say that it's incredibly difficult to learn the basics of the game. It's comparable to other teamwork based semi-strategy including games, that I'd dare to put all kinds of MOBAs here - it's easy to understand the basics, but there are some things you can learn along the way as you play, and you end up with certain gameplay aspects that one can master. Such things, like stripping the armor from the enemy ship before finishing them off with a mortar, or rebuilding red component with a spanner instead of a mallet, are not really much more difficult to understand than AP or AD ratio on your skills in LoL or Smite. One does need to put some effort to learn the game mechanics, though, and that's in GoIO as well as many other games, but I can't really say you need to put any more effort in this game compared to the others.
When it comes to matchmaking, ending up with lvl 10+ people may be frustrating, but there's a reason why there are 1 to 3 lvl novice lobbies in this game. I suggest joining open lobbies only after you lvl up all 3 classes to level 3, and then keep playing novice matches until you level up to level 4 with one class, so you can stay in novice matches as long as possible, and get as much experience in the newbie lobby as one can get, so you'll have a good headstart before stepping into actual, normal games.
Overall really nice review, I just can't help but wonder if your opinion about the game being too difficult doesn't actually come from not playing tutorials and not joining novice matches, for it is kinda obvious that a fresh newbie won't have alot of fun if he decides to join a game against a veteran with thousands of matches played, especially if he is yet to learn the game's basics, but neither was it intended for anyone to do something like this if they don't want to.
