I have worked on quite a few Ruby web apps and built quite a few myself. Maybe 3% of the cases I encountered were about Ruby not being performant enough to do what I needed it to do. Where did the rest of the productivity of end users get lost?

Org dysfunction.

Note that those were web apps - so the user did not have to install the runtime, dependencies etc. to use the software. That is a whole other story (and not a very merry one, at least for all the scripting languages out there).