I totally agree that the singleton detail is beside the article's point, but what is the modern case for singletons? It seems like singletons are now considered a synonym for global variables. What other purpose do they serve?
It enabled us to decouple some code deep down in our architecture and enforce some constraints around the use of this particular piece.
When you actually need a singleton it's best to use one and call it out as such so people know what they are dealing with. Dependency injection will often be passing around a singleton everywhere without people being aware that it's a singleton and all that that means.
I suspect dependency injection has the same problem: you could achieve the same results in a non-object-oriented language.