That's because the use case for classes appears when the information needed to understand the program exceeds the programmer's working memory. At some point, you need some way to make something into a black box whose innards you do not need to understand when not working inside the black box. Languages which do this badly do not scale well.

This is a hard problem. We have, at least, structs, classes, objects, traits, modules, and namespaces. There still isn't consensus on how best to do that.

At a higher level of grouping, we have more trouble. This is the level of DLLs, microservices, and remote APIs. We barely have language for talking about that. We have no word for that level of structure. I sometimes refer to that as the "big object" level. Attempts to formalize that level have led to nightmares such as CORBA, XML schemas, and JSON schemas, and a long history of mostly forgotten interface languages.

It's interesting to read that the author likes Python's new typing system. It seems kind of half-baked to have unenforced type declarations. Optional type declarations, sure, but unenforced ones?