The valuable parts are strong typing, code reuse, and sometimes metaprogramming.
Many modern languages include many OO features but don't advertise them as such because too often it induces a religious reflex, like shouting "socialism" in America.
The OO paradigm is much more fundamental and natural to the way we think of and model Domain Concepts/Objects. I remember studying fundamental techniques like CRC(Classes/Responsibilities/Collaborations), Commonality/Variability Analysis, Rumbaugh's OMT etc. and thinking how natural it felt to model domain concepts directly in code. People seem to have forgotten all that and only focus on fads/acronyms like Patterns/SOLID etc. without really understanding how they came about and what their nuances are. The result is that people don't think through their analysis/design but merely follow a cookie-cutter approach popularized by some self-aggrandizing author and when things fail blame the OO approach.
