Not "is a," but rather, "may be." This is because I never personally experienced the problems noted in the link I posted, but they are coming from what appears to be a credible source. You mistook a suggestion of problems for a personal conviction.
No, that mistake typically is a result of somebody faulting Ruby for Rails' problems. As the parent to my comment said,
Rails: Here's a kick-ass hammer, a kick-ass saw, a kick-ass measure tape, etc...
My point is that those kick-ass tools may be made of balsa. The editorial that I linked immediately came to mind because it too used tools as an analogy.
If Rails were a toolbox, all of its tools would break under duress. Regarding Ruby:
"And furthermore, for me, programming languages and their runtimes are tools. I think they are for a lot of us. You wouldn’t continue to use a hammer whose head keeps flying off when you take a swift backswing, would you?"