The biggest problem with OOP is arguably inheritance, specifically implementation inheritance. The basic issue is that "protected" methods may be extended arbi

The biggest problem with OOP is arguably inheritance, specifically implementation inheritance. The basic issue is that "protected" methods may be extended arbitrarily by a child class, with zero indication of what properties might in fact be relied upon by methods in the parent; this inevitably leads to a rather intractable version of the Fragile Base Class problem. This pitfall of open-ended implementation inheritance (a.k.a. "open recursion"), which is precisely what "inheritance" per se provides over the well-known (and often used) combination of "object-based" composition and "interfaces"/traits/type classes, is pretty damning for OOP itself.