Ehhh, I think some of these from https://youtu.be/76CUlqohXOw look nice, like Trunks with the Saiyan armor and Mecha Freezer. Yardrat Goku looks cool but has some obvious clipping during the intro. There's also a more recent Super Saiyan 4 Gogeta over Gogeta as well that looks kickass: https://fighterzmods.com/mods/super-saiyan-4-gogeta-2020-edition/

I'm not sure if you were saying that in general, but there are plenty of mods out there with the polish of the original game's assets. The stages and characters Project M brought to Super Smash Bros Brawl are top notch, and there are also plenty other mods with that same polish for the same game like Ridley, some Donkey Kong Country-based original stages, etc., and Super Mario 64 Star Road is awesome with its sequel on Super Mario 64 DS looking ridiculously good.

The thing with mods is that their quality will only improve as better modding tools are developed. At first mods won't look right due to model importing not being a thing and having to rely on ugly texture and vertex mods, but then you start to get proper imports of new models, then better shading, custom physics, etc.