Part of the problem is that fossil is very opinionated. It's great if your development flow is similar to that of the sqlite team. But it is very difficult to get it to work for other workflows. And in particular, fossil is designed for use by small teams and isn't really designed to be used by large organizations. This is even explicitly mentioned in the "Fossil versus Git" page (https://fossil-scm.org/home/doc/trunk/www/fossil-v-git.wiki)