How to speed up icloud photos downloads on PC?

I'm trying to download all my photos (50GB) from icloud as full resolution images on my Windows PC, but it is frustratingly slow.

I select a few hundred at time, select "Always keep on this on this device" and then wait a looong time.

I can see in ethernet activity that icloud only downloads one item every ~15 sec which is utterly dumb. I have 50Mbps download so can cope with significantly more. How can this be made to go faster? I've been at this for over a day and still nowhere near finished.

It would also be helpful to have a single button to download everything and just leave it churning in the background. Why isn't that an option?