PWAs were more than an experiment - they were even mentioned in Apple keynotes (IIRC). And sandboxing was every bit as stable as website sandboxing.

They were killed because app store operators realized they bypassed an ability to police payments that could not be monitored and (effectively) taxed.

This was a technology that could have been successful in any environment where a merchant's freedom-to-request-direct-payment was protected. In such an environment, it would have shifted incentives that apps now become a burden on developers as well as on Apple and Google's review processes, and PWAs would flourish.

But that's not the environment we were in! And arguably, even post Epic's litigation, we aren't fully.