Right now one of my hobbies is robotics/electronics/makerish stuff, and most of what I've learned has come from youtube/reference documentation/blog posts (I bought a few textbooks as well, although most of them are collecting dust). There's a bit of a social aspect in that I'll ask friends with actual EE degrees for advice sometimes, but even then I mostly get "ah I haven't used that in forever, I don't remember". Most of my learning is by setting a goal, and then more or less learning the skills along the way. I don't know if it's efficient or not, but it's not costing me anything other than time.
The other thing I've been teaching myself is art techniques, and you probably guessed it, I've learned those things in the same way and through practice developing my own style. Again, no institution needed.
Don't get me wrong, I think institutions and the social aspect of them can be tremendously useful, but if you want to learn a skill and you're interested there's practically nothing stopping you, you don't need them, it's just a bonus.
