You can reply and interact on platforms from an RSS reader. All an RSS feed is is a list of links. When you click them, you go directly to the platform. When using on a mobile device, RSS readers will even open the app for you to reply or interact with posts.
The fediverse will never replace RSS feeds. They serve a totally different purpose.
Wow what a great community idea! As more product reviews are added, it would make Lemmy more indexable to search engines as well.