Yeah I hear you, and I actually learned enough from those sites to become a daily linux user, but in terms of advancing my skills, I find the wealth of documentation available almost overwhelming. I know that everyone learns differently, and some folks can walk into a crowded library and find the tools therein to pick up new skills on the regular, but I personally benefit from course structure. For those like me in that regard, I recommend this course.
For everyone, who does or doesn't find the course useful there are of course the amazing resources posted in the 1 Year Linux Challenge thread: