> Even within some universities you will find graduates with completely different levels of ability despite achieving the same degree.

Agreed. Even without considering students’ motivation and skill, sometimes this is just caused by flexibility in the degree design. Some universities offer students a lot of choice in the courses they take. For example, I chose not to take the algorithms class (I decided to self study it at that time) and instead took the graph theory class. It turned out that at that time my self-studying overemphasized algorithms likely asked in interviews (like greedy or dynamic programming) but didn’t cover more theoretical aspects like P/NP, pumping lemma, etc. This was something that I started regretting years after graduation.

I think offering too much choice to students who were still learning is probably a mistake.