Mozart/oz allows you to easily implement actors which also have OO inheritance.
Generally, many superior programming paradigms (logic, constraint, functional, concurrent) have been ignored by the computing industry which has probably cost it billions of dollars in lost productivity.
Furthermore: ""When an actor requires a reply message from another actor, it is known as an insensitive actor, and will not process any further messages in its mail queue until it receives that reply.""
Why must this be so? In Io, the same objects/actors can run other coroutines while waiting on a message.
Just because no language happened to implement all of these in the 1970s and does not mean no language could have implemented them. In the concluding paragraph the author does go on to say that it is now possible to do all these, but I disagree with his implication that it is advancements in technology that made it happen. A more likely explanation is simply that programming languages are notation, advancements in notation do not follow the exponential curve of Moore's law, and it simply took this long for people to think of combining all these concepts in one notation.
An additional example of that symptom was an article posted here in the last couple of weeks that said effectively "To improve your IT career, learn to negotiate with vendors." This is to me is a problem orthogonal to the choice of language or development practice.
For another take on this, consider all the interviews in Coders at Work. These are at the top of list of productive programmers of today. Some of them wrote in C, some despised C++ and C, none were methodologists.
Although that little bit of static typing would probably have dealt with the vast majority of expensive null-pointer bugs.