Go ask WoW how well it worked out for them to add randomized stats on gear.

Oh wait, you can't because pretty much everyone left the game because of randomized stats on gear...

Mostly, because while it sounds fun in paper... In practice you end up facing like 0.01% chance to get the item you want, with the stats you want, with the slots you want, with the tertiary stats you want, that's Titanforged... Etc.

Honestly, I'd much rather have "Blank" items that you fill the stats in yourself via Materia. Then you get to alter your own items stats instead of playing with RNG. Also, you get to use some of the 10 billion Materia the game throws at you these days which would be cool...