In my experience all large or very large scale apps upgrades (and I've done quite a few) are complicated in a way or another, no matter the stack. Technical debt stacks up in subtle ways (dependencies get obsolete, a specific feature used the framework in unusual ways, stuff can be rewritten with more built-in framework features etc).

I don't see how this article would give Rails bad publicity, personally; I'll add that the advice they provide is pretty much what I would recommend for any tech stack too.