I'd say the change log in something like VisualWorks was definitely not git-able in any way that would facilitate merging of several developers code. In fact it was extremely difficult to keep images in sync without something like Envy/Developer.
Lisp to me is like a fascinating fossil.
Doing Git with just that seems only a little different than what we'd do with a collection of source files today in some other language, including branches and merges.
At the same time, one commercial site I worked at was doing its SCM for C code using kludge scripts over SCCS to an NFS volume. The next was putting C and C++ into Apollo DSEE and making SPARCstations jump through hoops to use that (because ancient DSEE on some Apollo DN10ks for SCM and CI/CD was better than the state of the art almost everyone else was using) and my advanced R&D group had just gotten DSEE-descendant Atria ClearCase for greenfield work in C++ from our Sun and HP workstations. The next site was using some dumpster fire of `.BAT` scripts over Perforce(?) for Windows NT-dominated C++ development.
I'd say VisualWorks Smalltalk's wasn't the problem for team development at the time. The state of practice of everything else was more the problem.
Evidently you have some experience with Smalltalk, but what makes you say that about Lisp? Also which Lisp exactly do you have in mind? To me the Lisp family of languages is more like Classical music: it doesn’t satisfy some modern sensibilities, but it has a timeless elegance and will be around long after the latest fad is gone.
The major difference being the ecosystem built around something like C# is miles ahead of anything available for even Clojure. Some people might think that's an advantage, but for people like me whose job is to be pragmatic and "git er dun" it's a major impediment.
Hence, lisp has become a kind of toy from a golden age. I find myself reaching for C# or Python for experiments. I have dabbled in lisp occasionally over the years but never found Clojure very compelling.
It can also have access to the whole Java ecosystem or JavaScript ecosystem. Funny enough, it can also use most Python libraries. And if you're willing to go less official, it also can be used to leverage Erlang's ecosystem and recently Dart and Flutter.
Unless you meant something different than being able to leverage libraries, frameworks and some of the tooling?