Originally Posted by
Kumorii
Engine rarely dictates polygons and textures. It controls lighting and shadows, but that can also be "tricked" and baked into textures and such.
Difference is WoW is an MMO. MMO tends to have lower graphical fidelity due to performance reasons since there is a lot more going on than in a smaller game such as an RTS.
In todays days and age MMOs can look good, but WoW also have it's own style. They have updates the graphics numerous times but they still need to look like they all belong together. Updating all the models, all the textures, all the zones, all the assets will take a tremendous amount of work. More so than an expansion or, hell even 2 expansions.
In short, WoW has it's art style which it has to adhere too which was set back in 2004. Reforged is a remaster of an old game where models and textures and look is designed from the ground up with 2018/2019 standards.
If blizzard does WoW 2 someday that will be a big increase in graphical fidelity I'm sure.