alt Hacker NewsIt matters until it doesn't. Git is the "lingua franca" but increasingly I see team members use only git integrations in the IDE, the web interface (Azure) or say, the Github desktop client.
Those users wouldn't mind switching to Fossil if the graphical interface is reasonably easy to discover and use.
Features don't matter as much as workflows matter. If they can swap to a Fossil integration for their IDE and their workflow doesn't change (or maybe only changes to click a different icon), it'll be much easier to switch and thus more people will be able to switch.