FreeCAD is indeed quite sluggish when loading, but during modelling it's reasonably doable, except for some operations. Working with a sketch with several hundreds of constraints for example is a real pain, but once the sketch is finished and a pad is made, it can work quite decently with the generated 3D object.
Starting FreeCAD is also a pain. I consider FreeCAD still in early development (It's just version 0.20 at the moment, and V1.0 is traditionally regarded as the first stable version fit for general use (Inkscape also took a long time to get there...) I have a thorough dislike for those very slow loading Appimage containers, but the're easy to distribute and they "work" (sort of), and FreeCAD is being developed by a quite small group of active people.
I have never seen 20 minute load times for FreeCAD, but a few minutes is quite possible. One of the longest was a STEP model of an SMT PnP machine I found on the 'net.
... And during those load times My Ryzen 5600G is running on a single thread of it's 6 core / 12 thread capability. Even though multi core processors have been common for 10+ years now, programs that make effective use of them are still not as common as you'd hope.