The biggest problem for me always seems to be figuring out what I need to know, rather than finding the resources themselves. For instance, assume you want to learn how to make a simple web app, and have no experience or background in programming, CS, databases, etc. Figuring out where to start and how the puzzle fits together can be really daunting.
You start googling but can't figure out how it all fits together. Javascript, Ruby, Ajax, Python, Rails, Django, Flask, MySQL, heroku, html, css, jquery, bootstrap, appengine, aws, servers, browsers, APIs??? It takes some time to figure out what things even are when you are taking your first steps. Once you realize you pretty much need to know a bit of HTML to make a website, finding a suitable tutorial, while sometimes frustrating, isn't all that hard.
Most people here know how these technologies fit together, but as a beginner I didn't. It took some (frustrating) time to learn how the puzzle pieces fit together, what is optional, what is new, what is proven... etc.
This problem isn't isolated to programming. I think this is a big problem for a ton of self directed online learning. Lets say you convince yourself you would like to become the next Satriani on Guitar, but don't know what scales, triads, or chords are let alone how they are built. Should I concentrate on technique drills, songs, improvization, theory? I have met a huge amount of people who get very intimidated and end out just learning to play songs from guitar tabs, and never progress from a very superficial beginnner level.
Perhaps it is a result of people not wanting to dive in until they can put together a basic mental model of how things work. Regardless, the "roadmap to expertise" problem seems to be real and discouraging for people not willing to just power through it. Can teachers and Tutors be relpaced in providing the direction through the weeds? I'm not sure, but surely solving this problem could be lucrative.