I'll say this about "advanced techniques" like wavedashing or L-cancel or whatever. Yes, anyone who puts in the time can learn them, but the main thing you're doing is building barriers. In Melee if you actually can't L-cancel and you play a character who is not Jigglypuff or maybe Luigi I guess (not that Luigi is a viable character at all), you're wasting your time playing games. The practice you get is mostly useless because your moves have incorrect amounts of landing lag, and every little interaction or strategy you learn is mostly going to be wrong learning. The correct thing to do to improve is to stop playing anyone else and just sit in training mode until you have L-cancels down pat. If you don't realize this for one reason or another (maybe you don't know the technique exists, maybe you just haven't had it communicated to you how essential it really is), you can end up wasting a ton of your time and lose to a lot of people whose fundamental Smash skills are way worse than yours just because it's frankly too important to begin to do without. Something like wavedash is less core to every fundamental interaction working correctly so you can kinda play without it, but not knowing it again just impedes your development as a player since basically you're playing without one of the main important movement options so you'll be wrong learning what to do in so many footsies situations unless again you play like Jigglypuff or Peach who just care less about it than everyone else (or for "characters who are too bad to actually use", Zelda doesn't care either).
The long term effect of this is to largely turn competitive play into a more "elite club" style environment by making the more self-taught type of players less effective and enforcing more of a "if you put in the hours, you get some sort of minimum results" environment. Naturally, it shrinks the community as those self taught style players see what they might perceive to be skillful play just not be rewarded and thus are unlikely to see the value in investing in the game; that's your actual consequence. If my experience, this filter isn't really that important at all for truly strong players; those players win on fundamentals, and their mastery of technical play is just one element on a long list of advantages they seek out in all areas of gameplay so its relative importance is almost meaningless to them. It's more important to players who are fundamentally bad players who have done some grinding. There's a certain type of player who is really just a bad Smash player. This type of player is usually just not good at learning less defined concepts like mix-up or spacing or whatever and usually extremely low on adaptability to unusual match situations, but this type of player tends to grind away really hard so technical barriers are extremely welcome as those can often be reduced to a more simple hours in -> results dynamic that really favors this type of player. It's tragic in a way since doing this still results in a pretty low ceiling for these players (they can be filters on the players who don't put in the time, but these players still just always lose to anyone good); you could even argue that the technical barrier giving these players modest success is just giving them false hope as by clinging to it they prevent themselves from seeing any real improvement.
This is years old, but I know when Brawl came out, there were a lot of lower-mid level players in Melee who suddenly found themselves at the very bottom of the new Brawl scene as their tech skill suddenly was useless but they were still being burned by their poor fundamentals, and I'm fairly convinced those players formed the core of the "Brawl sucks" movement (though if they'd stuck around, I'm sure they could have all made excellent Ice Climbers mains). That's just me recounting what I saw here; I know a lot of good players preferred Melee, but those who were really vocal I always noticed didn't tend to actually be any good at Melee either though they seemed to always really tout Melee's technical aspects. I'm not actually trying to come at anyone personally, but I would say that if you feel attacked, maybe some self examination would really benefit you. If you identify with grinding tech skill while lacking fundamentals and feel that you need tech skill filters in order to be able to win, it's not too late for you to rethink your approach to Smash and to start actually developing fundamentals; the first step to overcoming any weakness is acknowledging it! Watch your matches, actually think about why you lost without resorting to reasons like "I didn't use enough advanced techniques" but only using answers that are either legitimately poor strategy ("I needed to be poking way more with dtilt") or poor use of basic game mechanics (like "I frequently throw out fairs that are spaced too deep and thus unsafe on block"), actually make adjustments to your style in future games, and start actually getting better. Being actually good at any Smash game, including Melee, ultimately revolves entirely around fundamentals, and while Melee has a technical filter you're going to have to overcome, it isn't actually a road to make you a good player just an obstacle to overcome before you start on the true path so don't fixate on it! To be honest, you shouldn't fixate on any narrow game dynamic if you want to actually improve, but tech skill is perhaps the single worst thing to fixate on as it has probably the worst capability of any aspect of your game that you could focus on to compensate for lacking ability in other areas.
I think Ultimate made some really good decisions, incidentally. There's a lot of strategic value in a fast pace and having safe aerials, and Ultimate just cut landing lag universally without an input required. Being able to utilize truly high levels of mobility while being free to use all of your attack is really interesting and definitely makes the game more skill intensive, but there's no reason to require a precise button sequence instead of just having the player take off running so being free to use any attack while running is such a better solution than wavedashing. The best way for the game to be is to be very fast paced with an extremely high volume of decisions to be made but actually pretty low technical barriers beyond simply being able to consistently perform fundamental tasks with speed and precision; it creates an environment wherein the skill ceiling is very high but the barrier to entry is very low, and that is what gets you a very healthy competitive community.