You didn't go to the university campus first for your diploma, so this is your best choice.
In fact, universities are not as strict and mysterious as you think. University is a place with strong academic atmosphere but also strong inclusiveness. You can get to know some college students through work or business, and then ask about their curriculum, and then you can choose to take your favorite courses. This is not difficult.
Not only in the university campus, but also in the university town outside the campus. There are many small private rooms similar to teahouses outside my university. When the study room was full, we took our books to the teahouse to study.
Some things don't have to be experienced. Life won't give you a chance to experience, you can create it yourself. Sometimes, watching others pass by is also a very happy thing.
I hope you won't be immersed in the regret of not going to college in the future. What college students envy is your experience and experience.
I hope you are happy!