It’s there, pick Customise from the menu and drag the RSS icon into the bar. But they’re not interested in actively working on it – suggested features like hiding it instead of greying it out based on feed presence are closed due to a lack of interest. I think ideally they’re want it to be an extension.

"in a prominent way"

Don't they have that already? I remember it being a prominent feature for browsers ~10 years ago. Heck, even Outlook had a feed reader - still has it I think, though it's always sucked.

Firefox used to show a custom page when an RSS feed was displayed, but it doesn't seem to work any more.

Edit: it didn't seem to work earlier, but is working now after I added the RSS subscriptions button.