if you dont want to join classes then just dont join college, simple as is.
That's not how college works.
You don't always go to every class in college. In fact, High schools are generally more strict about attendances than colleges are because they're responsible for the wellbeing of minors.
In college, you have classes for your major course of study and classes that are electives. It's common for people to skip electives (and even their other classes). People often prioritize classes required for their major over electives, and skip one class while attending another in the same day.
You feel sick? You stay home/in your dorm. You decide that the class is stupid and a waste of your time? you stay home/in your dorm. There's an emergency? You're an adult, and you know how to prioritize things in your life. You fall into the good 'ol college depression? You get the idea.
The only thing holding you, as an
adult college student, accountable to classes is your grades and GPA. Not a professor or faculty member dragging you by the ear to class. Besides, IRL, many people can and
do pass their classes by turning in assignments, despite neglecting their attendance.
I know that for a Minecraft roleplay, it would be silly to expect or try for 1-to-1 realism in any area.
And I know that for Karakura, there are small high school-sized classrooms for the college classrooms, instead of large lecture halls that may host classes of over 100 students. So it
is believable for professors to care about attendance ICly to some extent.
But it is absolutely
hog wild that you could have a college character who ICly studies Art or Humanities, but they have to attend a
Traumatology class because it's the only class that's active at the time.
If there were a tuition fee for Karakura's college program, the majority of the time spent on the campus would be an insane waste of time and money because of the system of mandatory college classes.
(I do think there's a way to have college classes be mandatory and effective from both an IC and OOC perspective, but I'll save that for a proper suggestion forum)