The internet is still plenty open, people just prefer the path of least resistance
I firmly believe the best content on the Internet is not necessarily the stuff optimized for search engines and audience-building. We shouldn’t really care about that.
If you're blogging and worrying about "how will readers find me" you're doing it wrong, and are basically doomed to fail.
You blog because you like to write, and readers will slowly accumulate over time. Comments and/or a small forum can work wonders, too, as long as you're protected from spam.
I wonder — in absolute terms, is the number of people you can reach smaller today? It's surely proportionally smaller because the internet is much bigger.