Pardon me, but something I've thought about in regards to the whole argument on L-Cancels:
L-Cancelling does have a steep cost associated with it. Tech'ing. If you mash the L-Button for the duration of your aerial, or even just time it properly, you risk getting hit out of it and slamming onto the ground. Sometimes you tech instead of L-Cancelling because you got bopped, but because you weren't expecting to you techroll in a direction you didn't mean to, or you miss the tech window and suddenly, you're a very vulnerable target bounced on the ground. This is a problem that's very stark to me as an Ike player, as Ike both needs L-Cancelling and due to his slower aerials, is likelier to be swatted out of them if I space poorly. (If I had a nickel for every time I was punched in the chest during a forward air ... I'd still work on my spacing, nickels are meh).
The Shield button is extremely overloaded in Smash and thus carries a lot of risk and precision with it. You need to be precise and careful with your inputs, and yes, even hopping around L-Cancelling has a drawback to it. It's not one that it's immediately apparent, and requires your opponent to capitalize, but you can be forced into a bad position in exchange for the increased offensive prowess you get via L-Cancels.
That's my take on it, anyway.