Comment by muti

Darktable editing workflow is centered around modules. Exposure, denoise, various color adjustments, etc are all separate modules. Dynamic range compression (and other common operations) has several implementations: base curve, filmic, sigmoid, and AgX. They all essentially do the same thing but have effectively superseded each other as they were added to newer releases.

Darktable keeps the old modules around but hides them, opening a file processed years ago will still go through the pipeline with the base curve module and come out the same. As a bonus, it is possible to use "obsolete" modules that may handle certain images better, achieving a particular look, or you are comfortable with the older module and prefer not to use the new replacement.