Brawl is one of the most obnoxiously restrictive games ever made and that did nothing to stop good players from absolutely shitting on scrubs.
The most important thing is to make mechanics that are intuitive to understand and don't insert unecessary tech skill floors for things that don't need it. Slap city already majorly addressed melee's sometimes-silly execution barrier by changing L-cancels to something optional instead of something you want to do every time (L-cancels preserve landing momentum), you can do whatever you want out of a dash and turn around at any point without needing to cancel something, there's a configurable input buffer, etc.
Ludosity found a very happy medium with their last game.
Brawl was an unbalanced mess. We properly should talk about the more successful titles.
Besides that i agree and that was my intention with my first post in the thread. The game is clearly mainly target at a casual audience with competitive play in mind. Therefore skill should naturally evolve and not have "skill bumps", where player need to master an advance skill to become better.
L-Canceling is a good example. In Melee it is necessary 99% at the time and are just a skill check (which also wear of the player's hands ...). In Ultimate we have auto-canceling windows, where parts of a move's animation will cancel landing lag. So we went from a skill check to a knowledge check, which also can be easily balanced. This is something even a casual player may notice naturally in-game without the need of guidance.
This is something, i think, is the optimal design for a casual fighter with competitive elements. Take elements people like about advance moves and make them part of the normal controls. Attacking out of a dash, one advantage about Wavedashing , is also in Smash Ultimate besides Slap City. Increase movement options without the need of Wavedashing should also be a better solution for casual players then having advance inputs.
Another aspect, which should be unique to mascot fighters, is limiting the basic mechanics by design. Smash Brothers Ultimate shows, that instead of having many basic mechanics, it makes more sense to give fighters unique mechanics, so that they look crazy and unique on there own. For example there are five fighters with unique comeback mechanics, six with there own unique gauges and many moves or mechanics, which break the basic game rules. Similar how card games like Magic work, where some cards just break the game rules and turn the game around. Ultimate's DLC character all looked crazy to people in there reveal, since they look like breaking the game, but in the end there are (so far) balanced fine.
(I use Smash Ultimate as a good comparison, since it is well revised by casual and competitive fans and also is the best selling fighting game of all time.)