The game is...well, I hesitate to use the word "poorly" since it's not THAT bad (the game still runs after all lol) but for lack of a better term, it is poorly programmed. I won't even go into the numerous bugs/glitches since those are already well-documented (Blind, Magic Defense, etc). Then there's the translation of course, and also the fact that changing the button config doesn't actually work in two areas.
This isn't a knock on the game at all, believe me. It's more of a "wow it's great despite all the flaws."
I mean, that's relatively mild, given that it's a game from the unpatchable era. I know the game pretty well, and I've reverse engineered its battle mechanics on my spare time. It is all very elegantly written. There are tons of ways to exploit the game when you start to see how it works, like overflow into negative damage, etc. However, it's kind of just the way the game is, to me as a programmer.
Sure, there are bugs, but the same is true for all games. Given it being a relatively early and complex 3D game, I think the game is very robust. I don't think a few bugs is cause to say the game is poorly coded.