I had a dream once that I was playing Minecraft, but my inventory showed me absolutely nothing helpful. All I saw was a bunch of question marks.
Now that dream is a reality! Introducing the Cursed Inventory Challenge! A resource pack created within the span of an hour and 40 minutes!
Here's the gist of it: Loading up your new world, nothing seems amiss at first glance, but as you punch your first tree, kill your first cow, or raid your first village, you will immediately notice that all the blocks and items have been given the same enigmatic texture. You can't tell diamonds from charcoal in this condition, so inventory management is CRUCIAL.
There are two different modes you can try. The first is (relatively) easy mode, where all the blocks will have the same texture, while all the items get a slightly different texture from the blocks, but every item will still have the same texture. This is shown in the first category's screenshots. The second is a more hardcore mode, where blocks and items become indistinguishable, as seen in the second category's screenshots. Not recommended for people who have a hard time keeping track of Minecraft as it is... like myself.
Of course, I didn't change everything. You can't get command blocks in survival, so there's really no point to changing their textures (although I did do it for bedrock for some reason). Basically, everything you can get in survival Minecraft, expect it to look like everything else you can get in survival Minecraft.
Some screenshots! Here's for "Easy Mode":
Aaaand here's for "Hardcore Mode":