Don't buy it. The Wii came equipped with full BC and actual ports for GCN controllers.
You could use the Wiimote to play smash but it was absolutely not the intended method of playing, as the game itself would tell you. And even if it was....again.....they could have ported Melee to the switch and nothing would have changed for casual players. The control scheme is literally the same.
Sakurai said himself that many of the changes made to Brawl were made because of the limitations of the Wii Remote control scheme. Yes, you can use a Gamecube controller on Wii, but a good majority of the console's user-base, didn't have one, so the game still needed to be designed with multiple control methods in mind.
The only platform limitation in Smash 4 came from Ice Climbers. Physics has absolutely nothing to do with it.
If that were true then Smash 4 would be the slower game (needing to be played on a 3DS) and Brawl would have been more like Smash 4.
But it is true. You know Ultimate's "Balloon physics"? Those were originally intended for Smash 4. But were scrapped due to the limited screen size of the 3DS, hence the speed Smash 4 got stuck with. When Sakurai got the Switch, the larger screen meant the team was able to "up the tempo" in his words, as characters would be easier to keep track of on the larger display.
"This time, the screen is easier to see than the 3DS version, and it’s not just people who are not used to playing games, so we focused on bringing up the tempo of [Super Smash Bros. Ultimate]," Sakurai explained. "I think that sort of covers the characteristics of the series."
And besides, him talking about control schemes is a bit moot because he has admitted WAYYYY more times that he changed the game specifically for skill gap reasons.
Control limitations were one of many factors into Brawl's final game design. But skill gap was also another. Again though, what Sakurai means by that, was that he intended to design Brawl as a more approachable fighter for the Wii audience, which consisted of many newcomers to gaming. Brawl was designed to lower the skill gap, but it was mostly because of the platform the game was on, not some hatred for the competitive scene.
Regarding Melee, Sakurai has stated that it perhaps went too far in the "hardcore" direction, where it has the highest skill floor in the series due to its technical nuance. And while you can argue Brawl was too much in the opposite direction, It does show that he intends to make games that don't heavily favor either casual, or competitive sides. Just a game that can be enjoyed by anybody.
Ultimate IS Smash 4.....with better mechanics. Literally all of the changes to ultimate from smash 4 are to make the game more competitive.
When i say "gameplay" i mean mechanics like short hop, cancelling dash animation with normals, reducing landing lag frame data, increasing 1v1 damage, option to toggle Rage, ect ect.
None of that required a console shift.
Ultimate is what Smash 4 would've been had it been given better hardware and a more favorable time frame to work with. Sure, many changes are natural ones that come with a sequel, but many of them were also what probably would've been added to Smash 4 via updates. People forget that Smash 4 died so quickly, partially because the Wii U itself died so quickly. On top of being developed with an under-powered handheld in mind, the game was also too little, too late for the Wii U, as Nintendo would dump it just 2 years later.
What this meant was that, the amount of time the developers had to balance and fine tune characters, mechanics, and stages over the course of many patches to develop a healthy competitive scene was cut short. This left the game, in an awkward, half-finished state, ending with a broken DLC character, as Sakurai and the team moved on to start work on Ultimate. Regardless of whether it was more like Melee or Ultimate, Smash 4 was always going to have a short shelf life because the Wii U itself had a short shelf life.
It was far from the only complication, but it was one of many. Ultimate arrived very early in the Switch's life, and its on a much more popular platform. Which means the developers have more time and money to do bigger and more substantial updates to the game over the course of its life. It's also probably why we're getting another season of DLC Characters.
Smash 4, according to Sakurai, was intended to by a middle ground between Melee and Brawl, and you can argue he did okay for what he had to work with. But I think many will agree that Ultimate serves that role far better, largely because it's given better conditions to work with.