I think the lack of version pinning is a positive force in stability: reducing the pain of breaking changes increases the likelihood that library authors will break things.
With Lisp, I setup my libraries in jenkins to pull the latest SBCL and quicklisp distro once a month and run tests, it's pretty rare for things to break. Once or twice something with an SBCL release itself, once with a bug involving the interplay of two of Fukamachi's libraries. The SBCL one was noticed by others and fixed pretty quickly, for the library one I was able to use git-bisect to easily find the breaking commit and apply a local fix while I waited for the issue I filed to get addressed. This was during Fukamachi's life-threatening illness period, even, but an alternative maintainer did address the bug on their side. The only annoyance these days is Xach is suffering from who knows what preventing the quicklisp distro from updating since October, and there hasn't been communication with people offering to help, so it's forcing everyone to pull projects in locally (and qlot does help with that) for updates or use an alternative.