Wait... maybe... Linux not being a product... is the reason of its success as an alternative. And making it into a product... would make it lose what makes it different, the freedom to fragment and choose what you want from it. Maybe a company can profit from that. But Linux is not a product, there is no single enterprise behind it. Meaning also that is not made for profit. And also, that profit is not necessary, maybe not even wanted. Huh? Shocked, fellow capitalist?

The thesis here seems to be that if Linux just had a good (paid) "app store", then it would set up a feedback loop wherein professional apps would be ported, and that would bring more users, and that would bring more apps, etc. And, as a side-effect, all of the "rough edges" of desktop Linux would be fixed.

First of all, this isn't going to happen. It's clear that Canonical and Red Hat have no interest in operating an app store. And community-based distros are too understaffed to deal with setting up payment processing and all that jazz.

But more importantly, it's extremely doubtful that this influx of users wouldn't stall out immediately, because transforming Linux from a really great Unix to a really great business-user-focused desktop OS is simply a huge undertaking, and nobody has the time or community support to do it.

The fact is, Linux is working just fine. It doesn't need to change. Linux users are happy with it, and that's enough.

You want something that meets your expectations for what Linux should be? Start your own thing. (Search my comments for "Linux is a fish, stop trying to make it a bird" to see my suggestions on that subject.)