I also thought it a ridiculous statement fwiw. "The existence of a specialised thing means that attempts at building a general purpose thing is not viable" Apply that logic to anything specialised to see it. I'm really not trying to be rude or belittle you, I'm just trying to get a stark example that shows the thinking in the spirit of sensible discourse. You may read it differently and explain why and I'll learn something. So...

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.