I had a very similar experience in undergrad. I skipped all sorts of classes and got great grades. I didn't care. I put off studying weeks of material until day

I had a very similar experience in undergrad. I skipped all sorts of classes and got great grades. I didn't care. I put off studying weeks of material until days before the exam. I'd even have a beer or 2 before exams. It wasn't stimulating. For me, part of that was because I was doing the wrong thing the whole time. I was studying biochem when I should have been learning to code. When I went back for my masters in CS, I actually tried and cared. I think I missed 3 classes the whole time and only because I was too sick to go. Passion for becoming the best programmer I could be drove me to try harder and harder. While I know that school doesn't teach you everything you need to know about software development, I refused to let anything that I could learn slip by.