Ain’t slow relative to what exactly? it’s a slog of a game when compared to DMC, MonHun, anything by Platinum, ninja Gaiden etc
everything I can find online says that souls fans consider ds 3 to be fast compared to ds1&2 but outside of that, it’s slow when compared to non souls games. Also armor type doesn’t affect weapon speed which is easily the jankiest part of the game. Consecutive hits with a 1h sword in ds3 is slower than 2h weapons in most good games
Because weapon swings are supposed to be deliberate and purposeful. Putting weight behind each swings makes each blow more impactful.
Same reason there is no animation cancelling. Dark Souls isn’t supposed to be a power fantasy like a Platinum Game.