I have found Elixir as a whole to be amazing, but the debugging process to be painful. Maybe its because I'm used to using Chrome's developer tools (since I mostly debug JavaScript), but I really wish that debugging on Elixir could be simpler. Using printf's is just too painful and feels backwards.
Debugging in IEx is actually quite nice (https://nts.strzibny.name/elixir-interactive-shell-iex/), but I agree that GUI-wise there is nothing I want to use.
I would recommend you learn the dbg module that comes with Erlang. Its a great tracing debugger able to trace existing code in runtime without having to modify the source. There are also several wrappers on top of the Erlang tracing tools, like Recon for example.
I found Elixir extremely easy to learn (despite having no Ruby experience, nor any significant experience in any functional languages). I went through the (excellent) official tutorial in a couple days, skimmed parts of Saša Juric's book, and felt reasonably confident diving in to actually writing code. Within a couple weeks I felt like I "got" OTP and idiomatic Elixir.
I do agree that, at least for somebody who uses Intellij IDEs exclusively, the lack of good first-party support sucks. I do most of my debugging via unit tests and "printf" because the Intellij Elixir plugin's interpreted mode is just too slow for the debugger to be useful to me.