I’m not the only one then: I used to use Capture One as a companion to darktable, as documented here (A bit of a comparison between between Darktable and Capture One). But similar to you, I have found Capture One to have grown slower and slower, while Darktable has become faster. At this point, Darktable is actually faster than Capture One on my M1 Mac.
Truthfully, I edit most of my images in Lightroom these days. It just works faster for what I do most of the time. But whenever there’s a detailed or important job to be done, I’m using Darktable. There are a bunch of things such as saturated highlights or complex color gradings, or dialed-in sharpening, that no software can do quite as well as Darktable.
Being a software developer myself (in image processing, no less), I have bought licenses for most current raw developers at one point or another. But the only ones that made the cut are really Lightroom (because fast) and Darktable. That’s a truly awe-inspiring achievement!