Banks don't have to restrict their apps against unauthorized Android builds and rooted devices with Play Protect but they do. There is nothing to gracefully degrade when your goal is actually to just restrict access.
If we're willing to give that stuff up in order to bring native apps back to the web, then we can save a lot of time and effort and just redefine the web to include mobile apps and get Google to re-label all the native apps in the Play Store as webapps and change nothing else. Then those apps will technically be on the web! No developer changes even needed, the web won! /s
The problem is not that the banks aren't on the web. The problem is that the banks deny user-agency. That's the problem I want to fix by bringing apps to the web. My goal is not to get the bank app served over an HTTP request, I don't care about that part. I don't care if the bank's interface was written in Java or Javascript. I don't care if the bank is caching data in service workers or on disk.
My goal is to get the bank app to respect user-agency, that's the part I care about.
If we make the web into a native environment, then it doesn't matter anymore whether or not app developers are using it. The web forcing developers to support user freedoms is the primary reason we want webapps. The web is a means to an end, not an end in and of itself.