Yep. AppCode and Rider aside, the functionality of all other JetBrains IDEs can be replicated with IntelliJ IDEA Ultimate. I have to say that I still like the language-specific IDEs though because they are a lot less bloated and the default configuration fits a lot better.

They are, mostly. I think Rider is the one that you can't simply use intellij for. Other than that, it's mostly just convenience features and debugging. Eg intellij doesn't debug Rust, but Clion does.