Hmm. As a crotchety old man (well, I'm 32, but still), I hadn't even considered mobile. I was thinking Windows/macOS/Linux native apps as the probable alternatives.
In either case though, I think this is just one more reason to hate Web Extensions. I don't want browsers to win over native applications. (Of course "applications" that are little more than a bundled browser are even worse, whether on mobile or desktop.)
@ebruchez is right. Also by win, I really mean to compete head-to-head with the native platforms. I love a good native app as much as anyone. The recent Epic vs. Apple fight shows that we need more open alternatives like the web platform. Ones that are free to develop for and free to distribute. I'm looking at you Apple, charging me $99 for a developer account just to distribute a Safari 14 web extension in the app store.
In either case though, I think this is just one more reason to hate Web Extensions. I don't want browsers to win over native applications. (Of course "applications" that are little more than a bundled browser are even worse, whether on mobile or desktop.)