It's been the better part of a decade since I last revisited this on the Wii VC, but I distinctly remember thinking that the light platform-jumping in the overworld, a fixture of all Mario RPG series, has not aged well at all due to the clash between the D-pad and SMRPG's isometric perspective.
It's otherwise a fine game and certainly the fourth SNES JRPG I'd push on anyone after the essential trinity of Chrono Trigger, EarthBound, and FFVI. As far as Mario RPGs in the classic JRPG battle format are concerned, Superstar Saga and the first two Paper Marios have upstaged this game in most respects, and I'd recommend them over SMRPG as the more essential titles for someone who just wants to dip their toes into this category and see what the fuss is about. But SMRPG's fundamentals are still quite sound (it laid down a lot of conventions for how a Mario RPG might work, after all, and got a lot of them right on the first try), and it distinguishes itself with the recognizable flavour of a Square title.
Shame about the occasional isometric platforming, that's all. It sticks out like a sore thumb whenever you run into it. Later games deliver on the promise of Mario-reminiscent overworld interactivity far better.