I often have to teach basic OOP concepts to junior - mid level developers.

Many who've entered the career in the last decade or so seem to have missed what I 'd consider to be quite a fundamental grounding.

Not even advanced concepts from the gang of four book - though I have taught these too - but often just an un-awareness of OOP in general, even simple things like understanding encapsulation.

Frameworks and languages do evolve, but never being taught basic things like encapsulating state or exposing dependencies seems an issue. Very differnt from my own time as a junior when this stuff was constantly hammered home.