Ok, but then force Android and macOS to unbundle their crap. Why do I have to use Chrome and Gmail as default? Why do I get force fed iMessage, Safari and iCloud?
What it could lead to though is some real investment in Safari from Apple's part, which is very much needed considering how buggy and behind competition it is. That way maybe the web will indeed be able to compete with native as they already falsely claim it can.
You don't... You can have Firefox and Outlook as defaults if you want. Ever use a Samsung phone? It comes bundled with a bunch of Samsung and MS crap, despite being Android. Samsung has their own web browser, their own store...