Material design isn't very suitable for the desktop web... and I'm not even sure it will work on mobile but let's hope it will.

Firstly, it's too constraining, too specific, this style could get pretty boring and bland if every app uses it. And for lots of apps (and majority of webs), different spacing, structure, etc. is optimal – forcing them to use a different spacing would lead to worsened usability and ugliness.

Secondly, the animations can get annoying and distracting quickly.