I think it's that the things learned in school are academic (red-black trees, dynamic programming, writing toy OS and programming languages, etc.)

In the real world you're faced with building five nines active-active systems that interface across various stakeholders, behaviour has to be eventually consistent, you've got a long list of requirements and deadlines, etc. It's practical, hands on, and people are there to build the thing with you at a scale that far exceeds the university undergraduate setting.

It's not a bad thing, it's just different.

Students shouldn't be afraid of it. Your job and coworkers, if it's a good workplace, are there to help you succeed as you succeed together. You learn and grow a lot.

You also learn how to deal with people, politics, changing requirements, etc., which I would imagine is difficult or impossible to teach without just throwing yourself into the fire.