L-canceling is cool because it serves as the perfect "gateway tech" for new players. If you're trying to teach your friends stuff, it's really, really hard to show them wave-dashing and have them immediately apply that to their game. Even things like DI can be pretty abstract, and they might just say "oh yeah, I already do that" when they don't, haha.
But L-canceling is something fairly easy that makes a ton of sense to anyone who's playing Smash. When they see how much faster it makes them, they're gonna be really excited, and they're gonna wanna master it. It also gets them to begin to accept that there are harder, more cryptic things hiding in the game, and that mastering these tricks will help them improve in really interesting ways.
If it was removed from the game, I think the skill curve would actually be much sharper for newer players. It'd be like "practice your spacing, reads, and other fundamentals... alright now who's ready to moonwalk?!!??!" and their minds all explode.
Don't think of it from the perspective of a Melee vet. We're all going to L-cancel anyway - if it was removed tomorrow, we'd still L-cancel every time we landed. It's baked into our minds forever, hahaha. (Seriously, who else has been air-dodging constantly in turbo because of that? I CAN'T MAKE IT STOP). Think of it from the perspective of a player new to the competitive scene, and what shape their growth and experience is going to take.
The L-cancel might seem like a non-option in a competitive environment, because it is (there's never a reason not to do it), but it's a really important option for growing players, and because of that alone, I think it should stay.