EWh. There are still RSS alternatives and at least most sites (if by no means all) still have RSS feeds.
Now, you might argue that "But Google Reader was the de facto standard and mainstream audiences didn't know to just use something else."
However, unless they were reading RSS in the background through a portal like Yahoo!, mainstream audiences weren't using RSS long before Google Reader was killed (if ever).
Explicit use of RSS through RSS readers was always primarily the province of journalists, analysts, researchers, and various other folks who wanted relatively unfiltered from-the-source on specific topics.
It also didn't help that individual blog content has tended to migrate to publishing platforms in general. I still write a lot but publish on my "personal" blog relatively seldom these days because visibility is so much higher elsewhere.