Minecraft is blocky because working with voxels is more fun when it's easy to work with them. Blocks are easier to work with than the free-form voxels you see in other games. Well, just to say, the game came out in 2009. And, the blocks somewhat made the game popular.

Is Minecraft supposed to be pixelated?

Minecraft is supposed to be pixelated, it is how it's designed.

Why is my Minecraft bad quality?

This is usually caused by a slow or inconsistent Internet connection or by a slow server. ... If you're experiencing slow performance due to connectivity, you may need to pause or stop any current downloads, change your network settings, or you may require a faster Internet connection.