I've studied recording at school for 2 years now
You may be getting into the wrong line of work, if you can't hear the difference. Do you have the same difficulty in the school studio (if they are teaching recording, I must assume they have some sort of facililty)? Hearing acuity can be learned, ordinarily. I'm an older person, and my hearing disappears at 15KHz, yet I can easily distinguish between 2 different small condensors, or 2 different large condensors, or between dynamics. I spent this last weekend recording acoustic guitar, and we were able to distinguish between fresh strings and 6-hour-old strings on the guitar.
Either your hearing needs to be tested or you need to do some serious upgrading to your listening/monitoring environment. There are lots of threads here about acoustic treatment, selecting monitor speakers, and so on.
To answer your question, this is what you are missing: there is are serious differences in the sounds of different mics, and, if you aren't hearing them, the problem is with you or your listening environment.