One benefit i found over rails was just some of the libraries were more modern. I'm not a backend developer, so maybe I'm just not skilled enough to know how to do these things, but I found rails libraries tended to be dated and missing more modern features.

Specifically I wanted to run both the API and website on the same server (since it was a small company), and with Rails the gem Devise didn't natively support both and while rodauth claimed to support both I couldn't get the build flag to work. With phoenix it just worked out of the box with the most popular libraries, allowing me to move on without becoming an expert in backend frameworks. I agree with most everything else the author said too, specifically about it being more performant and liveview allowing me to build more dynamic websites easily.