Maybe I’m old school, but I don’t want push notifications from my web browser.

I wish they completely disabled service workers. I don’t want some dumb news site running code in the background because I visited the site once.

Just when you're not visiting the site, right?

It's quite important/basic feature required in most PWA use cases. Such feature will result in number of apps shiped outside App Store. This is probably why they delay it.

That's fine, you can just not subscribe. But other people do want push notifications, like for emails.

Also, notifications can be used to replace emails. Instead of being sent an email from a forum when someone replies to my comment (with a link) - I'd rather have the browser do that (with my permission).

This is how apple.com looks like on Safari (c) by Apple: https://ibb.co/ct6LTB0

How well does the page render on a legacy version of IE running on a Mac?

That's Safari for Windows. Safari for Windows was discontinued in 2012, almost 8 years ago.