The reason 3s feels stiff is because sf4 is so forgiving. 3s is unbelievably crisp and ridiculously responsive feeling once you get used to it. Link combos in sf4 may be timing strict, but in 3s everything has an element of timing to it due to the faster game speed, and what links there are are even harder to hit.
Sidestepping this game means sidestepping the greatest sf game there ever was. Up to you. Yea it takes a bit to learn but what fighting game doesn’t these days? I couldn’t pick up ST right now and expect to roll face without putting time in to learn the meta game to some extent.