“Ok” I generally associate with being adequate but could obviously be better. “Mediocre” is just inadequate.
“Mediocre” is one of those words where common parlance doesn’t quite line up with the textbook definition. e.g. from the Oxford English Dictionary: “Of middling quality; neither bad nor good...”
Some synonyms for mediocre: decent, middling, ordinary, so-so. It can mean inadequate, but it can also mean adequate.
I’m just talking about how I view/use it.
Another common synonym for mediocre: has no place on a software development team. Not technically correct, admittedly, but that's how I read that word in an software engineering context. Adequate is not good enough.
I probably should have written it as “OK Engineer--“