> In fact Safari has often been the best mobile browser

There are no other browsers on iOS. When you are using Chrome it is using UIWebView (in other words, it is forced to be a crippled Safari due to anti-competitive policy). Although recent Chrome will be using WKWebView which means at least it's same as Safari. The UI around the browser is not the browser.

> Few users cares for logging into some website from mobile Safari just to get a subpar experience over a native app (or a hybrid app),

Few users could tell any difference between native app and web app running in a browser that has modern appy capabilities, provided there is same quality of implementation. The only thing that can make the experience subpar is precisely the lack of capabilities.