Also how long have you been studying languages? I ask because I am curious if you think that the web, and later, apps, like Duolingo for example, can make a huge difference versus the pre-web era of language learning. Pre-web, I would agree with anyone that yes it would be extremely difficult to learn a language on your own unless you had traditional schooling. But today there is nothing a traditional course in German could give me that I couldn't get from Deutsche Welle, for example (but I also realize there isn't a 'Deutsche Welle' for every language).
Sorry if this is going further than you wanted, I am just trying to get different perspectives and it seems like you have a good grasp.
I started studying in middle school. I haven't tried the online stuff you're talking about. I'm not sure that they would be just as good.
If while you are there, and are aware of any similar websites like that for any other language I would love to know!
You might be able to reach similar levels of language proficiency without the courses but the biggest problems are 1) finding hours and hours a day to drill writing characters and other mundane aspects of learning 2) guidance from an instructor who can tell you whether things that look/sound right are. And also I think a university course also gives you a survey of the literature and culture of that language and insight into it that would be hard to acquire on your own.