Slic3r doesn't really see much development anymore, with the latest release more than 5 years ago.

https://github.com/slic3r/Slic3r

PrusaSlicer has added a lot of features since then. Even Bambu's slicer is built on top of PrusaSlicer.

It was based on Slic3r, however I urge you to diff the sources to see how much has been rewritten and extended. Plain Slic3r is too far behind both PrusaSlicer and Cura nowdays.