N64 textures dreadful? I guess you must be a fan of the horrible wobbly and pixely PlayStation textures then...
While it's true that the PSX had a bit higher res textures, atleast on the N64 they were smoothened out and didn't warp around like crazy.
Notice how after the first proper 3D accelerators (3dfx, Rendition, etc) hit the PC scene those sort of effects became the norm for 3D graphics on PCs and later on the other console systems too, including the Sega Dreamcast and PS2.
PSX and Saturn style 3D visuals were fine for the mid 90s, after that they got a decidedly dated-looking feel to them.
Nowadays, there's a lot of talk about the "pixel art", but I can assure there was no "pixel art" back then - the non filtered 3D graphics were considered worse-looking by gaming enthusiasts, unless we were dealing with games where 3D acceleration was unnecessary like Doom.
I find it a bit ironic when I see people connect these old 3D systems to there modern 4K screens, using hardware mods to get the sharpest picture out of them only to reveal horrible dithering artifacts and similar unwanted things.
The fact is that these systems were designed with component output in mind, for either NTSC (480i@60Hz) or PAL CRT (576i@50Hz) screens that hid a lot of what was poor on the graphics.
With that said, a bigger texture cache on the N64 wouldn't be a bad thing, it certainly helped the DS.
My personal issues with N64 were more about the framerate drops and fogging, both of which could be attributed to a slow Z-buffer performance which had to be disabled for best results.