I don't want to make another thread when this exists, so I'm posting here.
I feel like Ultimate's tentative (because this can all change in the future) handling of landing lag was only a half-measure in an attempt to address the post-Melee lack of L-canceling. The main issues of post-Melee's lack of L-canceling are twofold: it slows down the game due to putting a damper on air-to-ground combos, and it removes the engaging element of being aware of the environment and thinking in response to that. As can be seen, universally low landing lag only addresses the former issue; the latter issue remains.
That said, bringing back L-canceling in its pure Melee form is just as flawed a solution, as it entirely depends on pressing a button at the right time, and there's no reason to not do it. Even if they added more landing lag to a missed L-cancel like some Melee and PM mods do, there still would be no reason not to L-cancel. Being punished for missing something you should have done anyway doesn't really sit right in Smash, especially in the Brawl-and-onward period of the series.
What they should have done, then, was to combine the best of both worlds into one option: On-hit L-Canceling.
This way, aerials would be handled thus: if the attack connects (either clean hit or on shield), it gets less landing lag; if the attack entirely whiffs, it gets more landing lag. It combines the faster pace, shield pressuring, and combos of L-canceling with the ease of lack of input and punishability of normal landing lag. Reads would be important in order to force the opponent into an unfavorable position, awareness in relation to the playing field would be important because low-to-ground aerials would be high-risk-high-reward, yet the attacking player still has the opportunity to execute and/or extend a combo.