I'm not saying the other characters wouldn't work with the Platinum touch, fuck yes I wanna see Serpico combos.
but with Guts, he will always use the Dragonslayer (or a large sword in general). I mean, the main reason why the Platinum touch works in a lot of games is because you can mow through mooks while learning and getting timing on the mechanics of the game. with Guts, if they wanted it to stick to feeling like YOU are playing Guts, you'd have no chance to test out combos as you'll be busy tearing everything apart in one hit. yes, I know boss fights like Zodd and Mozgus could have chances to use combos, but there's not really any other place for him to do it.
hell, even Mozgus' minions with demonic powers were torn to shreds easily.
Tbh you could still make a platinum out of it. With more enemies and a greater focus on platforming or more dark souls-esque combat that's more about positioning than actual dps since giant guts weapons kill most things in one hit. It could work.