Some of my classmates said that it hadn't in the sense that they already kind of knew what it had to offer and what to expect, but I immediately thought of how much easier and fun I was expecting it to b, as for me, I had expected it to be a lot easier and enjoyable.

I think the only thing here that feels a bit clunky is ¨was expecting¨, but honestly, I don't know if I made it any better, lol. You maybe could just say "...I expected it to be."

I don't necessarily mean I regret enrolling in it, i. In fact, I can't really think of any other major I would've wanted to choose, even though I do have some other career possibilities I would wantish to explore; it's just that I found it quite frustrating to realize that studying literature to become a professional means reading in a completely different way, not out of spontaneous curiosity, but mandatorily, where the only pleasure is in that beingof the satisfaction following the completion of a meticulous task, and also aiming to master a skill that renders a rather ambiguous and ethereal service to society I cathat I don't really feel I resonate with.

Some of my classmates said that it hadn't in the sense that they already kind of knew what it had to offer and what to expect, but I immediately thought ofremembered how much easier and more fun I was expecting it tooriginally thought it would be.

また、

Some of my classmates said that it hadn't in the sense that they already kind of knew what it had to offer and what to expect, but I immediately recalled how much easier and more fun I originally thought it would be.

I don't necessarily mean I regret enrolling in it, i. In fact, I can't really think of any other major I would've wanted to choose, even though I do have some other career possibilities I would want to explore; i. It's just that I found it quite frustrating to realize that studying literature to become a professional means reading in a completely different way, not out of spontaneous curiosity, but mandatoridoggedly, the only pleasure in that being the satisfaction following the completion of a meticulous task, and also aiming to master a skill that renders a rather ambiguous and ethereal service to society I cawhich doesn't really feel I resonate with me.

I'm not sure what you mean by "mandatorily" so this is my best guess.

We don't usually have sentences this long. It's somewhat difficult to read so I chopped it up into smaller sentences.