If Mojang had a problem with it, they would have stopped a lot of the super popular places that do it. Many, many, many people use Patreon or other donation apps for supporting them doing things like:
- Mods, including ones that optimize the code Mojang themselves wrote
- Resource packs
- Data packs.
Mojang is more concerned with charging for things like: access to an online server (no entry fees are allowed), or pay-to-win (diamonds for $$$, or anything that gives you an advantage over other people playing on the server).
Servers, as an example, ARE allowed to provide "cosmetic" benefits (with the exception of capes) to donators, but that's it. So, "Flame particle effect for $5" is fine, since it's visual and doesn't provide any inherent gameplay bonus. But a "$5 for Infinity/Mending bow" is not.
TL;DR: Since resource packs are visual, and don't inherently make the game bad for other players, the creators of those resource and shader packs are fine to do so.
