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.)