Cum Shite seems appropriate.

Anyone can build a bridge that stands, but it takes an engineer to build a bridge that _barely_ stands.

An engineer in and of oneself.

(Always enjoy when that construction is actually valid, people often miss the reflexive part)

It's that old joke:

"What do you call a student who passed their medical exam with the lowest grade in their year?"

"A doctor"

Not specifically the same but there's an adage, "C's get degrees". (I guess it's about how even if you got C's, you're still good enough to have a sheet of paper that even your class topper had?)

I always went with C is for cookie and that's good enough for me. Along with D for diploma.

But note, some schools require a C in prereqs to take further courses. And some schools may put you on academic probation/kick you out if your GPA falls below a C. So D for diploma is a sometimes grade.

C for competent (a higher level than 'degree')

In times past in Australia it was 3s get degrees, 4s open doors.

These days a 3 is no longer a conceded pass, it's a failure that entitles you to re-attempt your final exam.

Actually I had some good luck with hiring people that have the minimum marks and huge amount of outside adjacent skills. One example is someone who was running a manufacturing operation on second shift and completing an engineering degree at the same time.