Dealing with the security and privacy aspects of those would be enough to get near the complexity of an OS. And to note...looking at the facebook app for instance, being native doesn't seem to be a protection from bloat, it will there either way.
On the web as a static thing, sure 80% of the web is fine as a static information. The 20% on the other hand are things we care a lot about, and I personally hate the "why don't you install our app?" prompt on every damn site. Reddit is the poster child of this, and god no I don't want their native app.
To each their own I guess.
I look at the emails/calendar on the web _because_ I do not want notifications and other junk/distractions. I do not think it is big deal for people to have an email client app on their phone if they want their functionality.
I totally get that you prefer notification on your apps and no notification on the web, the same way people enjoy notifications on their watch and not on their phone, or only read their mail and calendar on their laptop and keep nothing on their phones, etc.
There is an infinite number of combinations of what people want, the whole purpose of these rulings is to let users manage the state they want instead of Apple dictating what is allowed or not solely based on their business interests, even if it those can align with your preferences for instance.
All this apple-related HN web-browser drama is not about what _users_ want, it is only about what app developers and companies want.
~80% of web usage is looking at web-sites, and most of them are already a bloated mess of JS. If anything, the web would be much better if more sites were like craigslist. That ~20% is not worth the cost in terms of privacy, security, complexity, battery usage. I would rather a native app, or use a competing service that provides one.