No one educated thinks that tech skill, in and of itself, is a bad thing. Hell, pressing buttons on a controller is a tech skill, and a non-trivial one at that (try handing twin sticks to someone who has never gamed before, and see how far they get in any game).
What people have a problem with is tech skill gone crazy, tech skill implemented for no other reason that to have tech skill. And tech skill for the sake of it is kind of antithetical to Smash, a series which prides itself on accessibility and simplicity.
Wavedashing wasn't a problem, as a concept and a method of movement. Yes, it's true that wavedashing added strategic complexity to the game, and had it done that in a simple, intuitive way, everyone would have loved it. But, it wasn't simple and intuitive. To perform it, you had to do actions COMPLETELY unrelated to the desired result; explain to me how it makes sense to dash forward by first jumping straight up, then air dashing into the ground. It made no sense, as a set of actions, and therefore was tech skill for no reason.
L-cancelling was the same thing. There was literally no situation in existence where you would consciously choose increased aerial landing lag. None. But, in order to halve the lag, you had to make an arbitrary and unrelated action upon landing (shielding). All that L-cancelling served to do was increase the number of inputs a player was required to do in order to excel at the game. It was an arbitrary APM increase.
And, this isn't Starcraft, nor is it Ultimate Marvel.
If wavedashing could be implemented in a simple, intuitive way, like double-tapping a direction, then it would be a fine addition to Smash's existing movement mechanics. There would be NO reason to dislike it, strategically or mechanically. But, until that happens, yes, I think it's perfectly rational in the context of Smash to dislike arbitrary and unintuitive tech skill for the sake of having tech skill barriers to entry.