LoL has problems, but to me they don't stem from a lack of action in the early game (in fact, I find there's quite a lot of action and the laning phase of every MOBA is by far the most compelling part to me). Limitations on what you can do breed a creativity to accomplish what you can with very little. I also certainly can't possibly imagine not wanting to win because of my character's development; I am good at MOBAs because I don't just "want" to win, I am driven to win. And I certainly don't care much about the state my character is in, except inasmuch as it enables victory. Gaining levels and buying items are a means to an end. Although, you can get all your abilities except your ultimate in about the first 2 minutes of any game anyway; having them all unlocked already is not actually fundamentally different, there will still be abilities that are better early and abilities that are better late, it's just a narrower band.

LoL's biggest problem to me is that it's been driven to a state with very locked-in roles which are hard to deviate from. To some degree the itemization has this problem, but it's mostly the jungle mechanics that drive in that game in my opinion. Or did, when I played it. Dota is much more flexible about both items and lanes/roles, even if people will bitch at any unorthodoxy still.

It's impossible to judge this without playing it, of course, but my initial concern would be that, if there are fewer paths to customization through items, and fewer things to consider (like gold management), the game would become too simplistic for the kind of time I put into them. I want a game that's essentially as complex as is reasonable possible without adding complexity just for its own sake. I want to be able to play a game forever and never stop learning more subtleties and nuances; a game with fewer core mechanics will always lean away from that.