The writing and the characters aren't on the same level as the old ratchet games. The writing, characters, and visuals in the Future games were amazing. It's not a case of growing up while the games stayed the same. Everything through A Crack in Time is amazing and this game does not live up to them in terms of the writing/story/characters. The difference is huge. The thought that this game is comparable to Quest for Booty in terms of writing makes me sad. Quest for Booty is on a different level from this (and most) games.And the writing is so bad I actually question whether I should have ever liked Ratchet, which is making me feel really bad. I turned the game off after the lines "el-oh-el," "epic fail," and "u mad bro" all came out me in less than 30 seconds. I'm scared to go back.
That being said, you should give the game a chance. While the writing/story aspects are depressing when compared to the older games, the game is really fun. I don't think the game is as dumbed down as you say it is. I have a lot of fun thinking about strategy. Especially in the multiplayer modes.