RSS readers allow you to collect the articles of specific sources in one app, making it a lot easier to find the content you’re interested in without crawling through a lot of noise. RSS (which may stand for Really Simple Syndication, Rich Site Summary, or one of several other possibilities — nobody seems sure) has been around a while, having been first developed in 1999, although it wasn’t more widely adopted until a few years later.
I use this as well, have mail/feeds enabled in Vivaldi with no mail accounts added. Then I just removed the mail and calendar icons from my toolbar, and now have a decent feed reader without showing things I don’t use.
That being said - I definitely accidentally deleted all my feeds at once in Vivaldi when trying to erase all received news stories. I’d recommend backing up the main Vivaldi config file somewhere occasionally!