I don't disagree with what you're saying, but the issue I have is with the monopolistic aspect of an app store... Basically, it's one or two monolithic companies that control everything and determine the rules because they make the base operating systems. With regards to updates etc, I think similar issues apply to native apps - e.g. devs can change the backend, which can break older front ends. I'm sure you can eventually have the concept of a versioned web app as well, much like versioned APIs, and users can decide if they wish to upgrade.
TBH i was mainly thinking about desktop applications where app stores are not really a thing (beyond Steam) and - at least in Windows - you can still use applications written a couple of decades ago while the companies that made them have long dissolved.
I agree about the gatekeeperness aspect of app stores too :-). At least with Android there is the ability to install APK files, though it isn't very user friendly.
