By actual standards, this game would be horrendous (the animations have no motion capture or anything similar, which is a little surprising... because the sprites in all the previous Mortal Kombats, were in fact, human actors doing "poses"... so you will expect something better for this 3D game).
But in the 90s? man this was considered a very good 3D fighting game by many. It was also the very first Mortal Kombat in 3D, sooo... it was considered a step up, just because it was made with polygons in that "pro-3D game frenzy era" of the mid-late 90s
(and that was the reason nobody cared a shit about Capcom's Street Fighter III by then, and almost everybody liked Street Fighter EX and its Plus revisions, made by Arika).
You can say MK4 was not that good... but it is fun. It is just a classic 2D MK... using polygons instead of digitized images.