The solution is for people to make web apps which are agnostic to platform and device, no?
There is no viable alternative to an Android or iOS powered smartphone for most people, and even switching between the two is enough of a challenge that few people do it once they've picked one. That gives their respective vendors substantially more power to fix prices and exclude competitors.
We have sandboxing, permissions, app scanning heuristics, and databases of bad apps. If the web works from a technical standpoint and security posture, so can native.