Yep, it’s not for everyone, and their docs are pretty clear about that. OTOH those same docs contain a variety of arguments that git isn’t really designed for everyone either and that fossil might be a better fit for projects that have just one or a handful of developers, which AFAIK is the vast majority of projects on Github. My experience is that it is certainly an adjustment but the docs are good at explaining (and justifying) the differences, and the built-in features are very useful, especially for anyone looking to reduce their dependence on a centralized host that’s become unreliable.