GitKraken is the best GitUI I've ever used. I highly recommend it. I use it for personal projects and at work. Professional License is really reasonable.
As much as i would like to agree with you, it should be a simple problem and there should be many comparable alternatives available, i can't because frankly all of the free clients in the wild suck in one way or another. I've been looking for years but everything i tried either looks like a cheap hack made with TkInter or lack one or two vital features. One might have a good branch viewer but lacks interactive staging, another client the opposite, etc.
I haven't tried gitkraken though, maybe it sucks equally much, my point is that there is an open market spot for good git GUI.