It might be the weakest of the jetbrains IDEs[0], but for a long time it was simultaneously the best Ruby IDE for my needs. It had reliable jump to definition when nobody else did. That was key for me circa 2015 when I was coming from Java and struggling with my first dynamically typed language since Perl. There are probably better Ruby editors out there now. I stick with RubyMine because I use jetbrains for other languages and like the consistency.

[0] I won’t say the weakest of their tools because youtrack exists.