I understand, this was my outlook when I left school too, but I changed my mind about that.
It took me maybe 5 years of work experience before I realized that no matter how "technically" smart I was, my technical skills were worth shit if I couldn't communicate better with my teammates. My writing was poor, I couldn't explain myself concisely, I could get flustered when someone didn't understand a point that looked straightforward to me... I had no notion of how I might go about convincing someone to do something I needed, especially someone who wasn't working in the same field as me or didn't have the same educational background. Not saying I'm a rockstar at this either now, but at least I understand the benefits of well-roundedness in a way that I didn't see earlier in my career.
I also see this with some of my younger colleagues now, who seem to care about technical output and cranking out smart stuff, but they're having problems communicating or taking feedback, and it's really clamping their future professional opportunities until they work on that...
Anyway - I don't mean this to disclaim your experience of feeling like you were wasting your time, and maybe the classes weren't the right level for you, just pointing out that at least for some people in the tech field, lack of skills in the humanities dept eventually prevents their professional advancement, hence it's not necessarily a waste of time for everyone to take classes outside of their major even if they're studying in a STEM field...