This is nonsense. I started writing several examples mocking this logic, but erased them because I think the original quote sufficiently proves the point.
Perhaps you should take the time to refute the logic.
I was surprised to see a comment like yours. If you can't be bothered to make a reasoned comment, then don't write anything.
The existence of nascar shows that attempts to build a family saloon has failed, if it had succeeded you could race your family saloon competitively on a banked oval track.
A general purpose thing involves a trade off such that it can do most things but can't do any one thing as well as something that is designed to do that and nothing else. Yes stupid car analogies to describe computing indeed. Totally. I'm sorry.
To me, the definition of a "general purpose" item is that it is suitable for a variety of uses, but not ideal for any of them. By contrast, a "special purpose" item is very good at one task, but performs poorly outside of that arena. For example, a "general purpose glue" is good to have around, since it will stick many things together adequately. But if you are joining aluminum to aluminum and want a permanent bond, you'd want to use a special purpose epoxy that is designed for this application.
As a parallel, consider the statement "the minivan is not a general purpose vehicle, as the existence of race cars (including F1 racers) indicates that all attempts thus far at building a general-purpose vehicle have failed." I feel this claim would be nonsense, because (obviously?) a vehicle that has been specifically designed for a particular purpose will perform better at this purpose than a vehicle designed with many other higher priorities.
I also tried variations of "a vice-grips is not a general purpose tool because it makes a lousy hammer", "Webster's is not a general purpose dictionary because it lacks full coverage of Latin medical terminology", and "a pencil is not a general purpose writing instrument because it will not scribe metal". But these all seemed so ridiculous that no one would claim they made any sense. So I removed them.
How did you find it insightful? Maybe "general purpose" is used differently between American and British English?
For me the logic of the statement came the other way round: we've got things that are focused on a particular task (accelerators) - because those exist it is clear that the general purpose things we have at the moment (CPUs) are not efficient at everything - if they were we wouldn't have accelerators (or they would be what we were using for CPUs).
Sure, we can't have a general purpose vehicle that is suitable for all tasks, but I can imagine someone creating a general purpose glue that just sticks anything.
Perhaps there is a processor design that can be efficient at every task - this article seems to be encouraging us to think about that problem.