Not the guy, but I used rails at my old job for one and a half year, and used it in some personal projects. I looked into Elixir(and Phoenix) during this time, and Phoenix felt like it was designed for more modern websites, where RoR is built for older and tries to adapt to handle modern ones. It just feels that when you want to do something more responsive in Elixir, it's designed for it, but in Rails, it feels like you're doing something unorthodox or something that is added as an afterthought. Obviously this isn't quite accurate, but it is the vibe I got.

Elixir is also a very cool language in a lot of ways. I wouldn't go all in on Elixir/Phoenix, but that's because there's not a huge demand for it, at least where I reside. I would 100% consider it for some smaller projects though, if I stood between that and Rails, and I wouldn't mind having to get more comfortable with Elixir.

Edit: I haven't used Rails 8, and haven't followed the ecosystem since a bit before, so not sure how this feels nowadays. I *really* enjoy Rails backend though, but the frontend stuff never quite clicked.