Half the people debating in this thread still believe that Lcancelling is fully mechanical. Please remember that there are many factors that you have to take into account, and that means sometimes you need to consciously Lcancel. Try playing as Ganon, or against the ICs. Or both of these at the same time.
Yes, in Melee, Lcancelling is always something you should be doing. However, it's also something that requires accurate Hit Confirming sometimes, a concept that I believe fights just right in any fighting game. Being able to Hit Confirm is one of the keys in not overextending and in being able to play safely.
Melee is not the only game where there are cancel mechanics, by the way. Have you guys ever tried to pull off a False Roman Cancel in Guilty Gear? Well, that **** is way harder than Lcancelling, that's for sure.
In my opinion, Lcancelling as a purely mechanical thing has to be removed from the game. However, all of the interactions that required precise hit confirming, such as pressuring a double shield, taking hitlag into account and so on, should require a NEW kind of technique.
Also, Powershielding is NOT always a good option. It's one of my signature moves in Melee, and I find myself regretting a powershield really often, as the extra knockback from PSing prevents you from being able to punish more often than not.
tl;dr : Lcancelling should be removed as a mechanic, and be automatic. But in the cases where your opponent could interfere with your Lcancelling in Melee, there should be a NEW technique that forces you to do something then and only then.
And powershielding is not what you guys think it is.