Part of the reason it comes up frequently is that a large number of educated, experienced programmers have decided that a toolbox without OOP is a better toolbox, than a toolbox with OOP.

But, it is difficult to throw out a bad tool when there appears to be no alternative that delivers its benefits. When that happens, when a tool is devised that delivers what OOP delivers without the problems -- such as the diamond problem, or the problem of having to decide "where" to put functions, or the problem of generic functions of more than one argument -- then at that time those very problems will become much easier for everyone to acknowledge.

The same thing will happen to classes and synchronous message passing, that happened to inheritance. In that case it took a while but an alternative came in the form of interface subtyping or predicate based subtyping, and then it was easy to see that inheritance was more trouble than it was worth.