Only elitists of either side say their way is the "true" way of playing Smash. To me, at least, this isn't a matter of casual vs. competitive, this is a matter of causing a schism between those who want it on and those who want it off.
It's all-or-nothing. L-cancelling is a huge fundamental to learn, and I don't see tournaments making auto cancelling the standard, between balance worries and, most likely, familiarity with Melee. New players now have the option of simply not learning it, which is kind of really bad if they want to move forward. If they make it permanently off and just have very low endlag for every aerial move, so be it. It'll get shit flung at it for not being Melee, but it's a better alternative to having a switch, in my honest opinion.