Just look at success for adults learning the things adults commonly take up: languages or musical instruments. There is some good results, but mostly you find people who can say "Hello, how are you" and no more; or they can play some simple songs but nothing major. It takes hours and hours of practice / study time to learn anything hard. You can find a lot of community ed classes that will bring you to about that level in many subjects, but it is hard to find anyone willing to put in the hours needed to learn something to more than a surface level.