Hi Dennis,
your specific example is downloadable. Just try this:

httrack
<https://mediasvc.ancestry.com/v2/image/namespaces/1093/media/4790350d-88c1-412b-81ba-8a260d67f13b?client=TreesUI&maxSide=500>
-v -s0 -F "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36
(KHTML, like Gecko) Chrome/74.0.3729.169 Safari/537.36"