Fact: Every fighting game with simple inputs flopped miserably
DNF Duel, Battle for the Grid, Tranpoo, Fantasy Strike. All these games are among the biggest, most embarrassing flops of the modern age of fighting games. Even the Arcsys cult can't keep half of these games afloat. None of these games have anything to offer outside of dumbed down special move inputs. Meanwhile, games like DBFZ, Mortal Kombat and even Soive are widely successful with the heckin' problematic DP inputs all these granola fiending, febreze gargling basedtubers loathe so much.
Fact: Street Fighter 6 was a huge success in spite of simple inputs, not because of them
Nobody bothers with the modern control scheme outside of the very bottom level of ranked play, mostly just because it's the default. The vast, VAST majority of players actively reject Modern in favor of the traditional classic controls and I don't think I've ever even seen Dynamic in an actual match. This is probably the only area you can say the game failed in good faith.
Fact: Casuals do not give a single fuck about simple inputs
This has been proven time and time again. Nobody will play your anime slop just because you dumbed down special moves. Nobody cares if you can do a single button DP in another boring ass anime kusomasher. These clueless zipperhead developers all look at Smash and think the reason those games do so well is because mario and pikachu can do DPs with a single button like it's not a game with fucking mario and pikachu in it. All these niggas have to do is just make a fucking game that feels and looks good, with aesthetics and characters that NORMAL FUCKING PEOPLE are actually interested in. This is why Kami 6 is winning, this is why Tekken and MK games run laps around dogshit like BB tag. Simple inputs do even less to help sales or player retention than Sajampog netcode. NO ONE GIVES A FUCK.