The major problem with relying on YouTube content for general automotive diagnosis and repair is that it doesn't tend to be general purpose. It's always "how this one guy fixed this one problem on this one car." A video could have a title like "Fixing a 2002 Toyota Corolla that won't start" but all it shows is the guy jumping right into replacing his fuel pump. There can be many other reasons that a 2002 Corolla won't start, but you're going to have to search through 100s of other videos to find the one that exactly matches your car's root cause, which you don't know until you diagnose it yourself.
The repair steps tend to range from so-so to excellent. The diagnosis steps are almost always very lacking.
Or they "fix" their issue by replacing the fuel pump, but totally neglected to point out what actually fixed their problem was the clogged pick-up sock they incidentally replaced while replacing the fuel pump. And never even looked inside the tank to address, let alone identify, their real problem.
Seen this kind of thing play out on YT too many times to count.
The repair steps tend to range from so-so to excellent. The diagnosis steps are almost always very lacking.