Yes mods proved than SE is slacking on some aspects of the game.
Mainly texture quality and hair designs.
Textures are client side only so there shouldn't be a technical reason for not doing it.
It's not going to stress the servers as the textures are rendered by your local machine only.
Modders made HD hair textures (for all current hairstyles), HD eyes, face skins and the difference is big.
Unfortunately all the mods are character based only so there are no textures for environments and other objects yet.
SE can provide HD texture pack anytime they want.
I guess they already have all the assets in higher texture quality and they just downscale them in the final implementation.
Even if they didn't they can make an HD texture pack.
If individual modders can do it that means SE can do it as well.
It's time SE to reconsider some things.
The expansion will come in late 2019. The game already looks badly outdated thanks to its potato quality textures and by 2019-2020 it will be a joke.