I believe much of this is due to the Erlang/BEAM foundations Elixir is built on. Ericsson has invested considerably in Erlang for decades, giving Elixir a boost in the tooling department.
I'm sure there are plenty of tricky traps that regulars have learned to work around and "just know how to use it without breaking it"; I have a suspicion a lot of unsatisfied people are those who come with different expectations of what the tool should do and how it should behave.
In these cases, they'll have a frustrating experience. I'd be interested to learn what it is so that we can make the whole thing better.
Ah good point. And rebar3 along with docs, and books are probably the first thing a newcomer will see when they explore Erlang the first time.