Indeed, good catch. It is too round and bulges too much, it's very visible in the strong plane change to the wrist. My boss also pointed out that the fingers are a bit too skinny in proportion to the wrist. It's tricky to work from your own body as it's so familiar you kinda become blind to details.
Leaving the other hand alone for now, my computer is too shitty to do fine details like the knuckles and wrinkles. I may revisit it later to fix the small issues, but I think I may be better off just doing new ones. Repetition is in my experience the best way to learn.
Here is the rough start on a second hand.
And my super shitty basemesh. I see people do sketches from rough box meshes like this so I wanted to try it. Seems to work pretty well so far, but I miss Slide Edge Tool and Insert Edge Loop.