This seems very much like a semantic debate. Either OOP is characterized by inheritance—which is consistent with the notoriously “OOP” languages like Java, C#, and C++<11 and probably the overwhelming majority of intro-to-OOP literature—or you exclude inheritance as a hallmark and make it so general as to be indistinguishable from many other paradigms, many of whom came before it. If the latter, why bother fighting the semantic debate at all? If OOP really is that unremarkable, why advocate for it as a meaningful label instead of advocating for SOLID generally?