The macOS ideal (and arguably it’s somewhat correct) is that you shouldn’t have to think about it at all. You should be thinking about the documents/content of what you’re doing, not the internals of the OS.

The closest they’ve gotten is iOS itself where apps sleep forever without your interaction.

In the very early days of macOS before becoming a Unix it was actually noticeable because for ordinary people they apps they would use would always be around, and it was still faster to swap in running apps than load a closed app from disk.