These resources often suck for the college major level anyhow. Youtube and such is all dumbed down usually. Or if it isn't dumbed down, you risk studying beyond the scope of the lecture. Every class I took, the professor would say something like "anything in lecture could end up on the exam." And indeed, every exam was comprised of something that came from the slides, and nothing that didn't come from the slides. Even if there was an assigned textbook, there would be so much skipped over, either subtopics or entire chapters. Emphasis can vary by lecturer for the same class as well. The class might fall behind or run ahead of whatever is outlined on the syllabus; that is more an aspirational goal than a solid plan of what to expect.

The best tutor, as always, is your TA or professor, during office hours that you already pay for in tuition. No one takes advantage though, well the students who were getting As already do just to validate their understanding. The students who really ought to go never go.