This is a programmer art pack, so it changes the newer features to be in the old Minecraft style, before 1.14. It's intended to be used on top of the programmer art option. This pack focuses on blocks and items, but there are a couple of entity changes, like for example the zombie villager texture that was broken after 1.14 is now fixed.
if you don't like one of the changes, you can go resourcepacks>retrospectacles>assets>minecraft>textures, find the texture, and delete it, or replace it using another file with the same name. I also included some alternative textures for a few blocks, blackstone, barrel, and mud, from before I realized they had Minecraft Dungeons equivalents I could replicate. For example, there's polished_blackstoneALT.png.
This should be up to date to 1.20. Some textures I didn't change because I felt they weren't too out of place, for example, the loom. I also changed sponge and lapis block to be even older variants, because I prefer those.
My twitter @ is SkarruBird, in case you want to see other things I do.