Are minecraft textures copyrighted? Can i just use the block textures in my 2d game?

Not copy righted.

Yes, to the extent they are creative and original works of authorship, they could be protected by copyright. They may also carry distinctive characteristics that serve as proprietary trade dress for a particular company.

They are certainly copyrightable, so assume that they are copyrighted. Try and find some textures you can lawfully use.