Honest reply, Minecraft's cube grid system and aesthetic has it appeal the same way as square grid systems do (e.g. Dwarf Fortress, Stardew Valley, RPG Maker). There is very little real competition for Minecraft in this regard, as most games don't dare competing with literally one of the biggest games ever. In turn, Minecraft has lots of untapped potential itself.
Here's someone saying "I bet I could do better" and just trying their best and making a damn fine product. I too wish the game would look a little cuter, but making game art decisions like these is not as easy as it sounds.