> a step so bold for an OS that even MSFT never even dared try in its worst Windows monopoly days
I don't think it's like "MSFT didn't dare to try", but rather "MSFT was too stupid to come up with the idea". They didn't have the ability to manage it either (and till this day their Windows Store app still sucks with tons of bugs). Not to mention that Windows was already wide open, never with a restriction "you can only install these approved apps" to begin with.
Basically, not that Microsoft didn't do it, but it couldn't.
Also can you imagine trying to download software over the Internet in the 90s? They couldn't depend on their users having high speed connections because most didn't. App stores probably couldn't work before 2000.