All the required math is online, of course
The problem is there is a difference between having proofs or definitions available and being able to teach yourself to understand the material.
(Well, a good textbook or expository webpage is more than just proofs and definitions, but wording quibbles aside---)
I don't believe you. There are many unfortunate people who suffer from cognitive disabilities such that they can't learn (e.g.) calculus from a book, but if you're reading this site, you're almost certainly not one of them.
If it's worth saying, but not worth its own post, even in Discussion, it goes here.