The question is, what does l-canceling add to the game versus having it manual?
Yes, I know there is a level of adjusting shield bubbles in order to mess up the opponent's l-canceling, but frankly that's within the realm of human reaction time, it's just a matter of increasing your tech skill further.
So what're we left with, the same game, just take years more to reach a point where you can play the real game. Then you have people who would otherwise join the competitive community not being interested because their initial impressions of the game are nothing like it actually is. It's not a lack of dedication, that's the point where the game is supposed to sell itself and it absolutely fails at doing so.
High tech skill requirements doesn't make the game better or worse, but often tech skill requirements (and burden of knowledge) have to be accepted to add depth. That said, it's a disadvantage for the game, so why would you want to increase tech skill unless it's necessary to add depth?
It's pointless. Melee was an amazing game (and yes, far better then brawl) but l-canceling was a terrible mechanic and shouldn't be in subsequent smash games, all it did was hurt melee's competitive scene. Future games should just have low landing lag.