It's reasonably common for me to start exploring a problem space, stub out a concept, and have a long drawn-out conversation with the compiler that touches many files, before finally reaching a point that is working enough to be interesting.
At that point, I can take a step back and note that actually, not all of those changes have to be made all at once, and I can break that patch up into a bunch of simpler pieces.
In Git, I have two essentially-equivalent choices:
1. stage the commit in small chunks, adding a separate descriptive comment for each.
2. commit everything as a WIP commit so this working state is in the reflog, then break it up into smaller commits with interactive rebase.
In either process, I'm able to get a better comprehension of my own thoughts along the way.
Fossil, refusing both staging would force me to commit the proverbial 500-line blob all at once, which is less helpful to the reviewer trying to discern my thought process.
If rebasing isn't important to your workflow, Fossil probably is a better choice for you than Git. It has a lot of comforts that I really appreciated even eight years ago when I did frequently use Fossil (distributed wiki and tickets are really nice, the web interface serving raw artifacts from any point in time is great for HTML5 game jams, SQLite is a very portable repository format, etc. etc. etc.), and I'm sure it's only improved in that regard. The only reason I use Git for personal projects is because rebase is that helpful to my process.