Auto scanning with border and angle detection works decently well [0], mini tripods with phone brackets abound. It’s very easy to set a phone above the table at a slight angle (that makes it easier to move the docs in and out and get rid of shadows) with the app auto scanning every sheet that’s laid below.
[0] I used Scanner Pro by Readle, on iOS for reference
I've changed my whole process now so it's not nearly as critical a step as it once was. But I still use it in passing.
Come to think of it a frame with a black base and an overhead light incorporating a phone holder would likely do the trick well.
And this seems more of a 'on my desk at home' sort of problem space than a 'whip it out of my bag' sort.
I think there is something to say about the sheer money size of the iOS ecosystem that allowed talented devs to get a decent ROI, even on niche apps.
I am happy with an android phone, but only because I also keep other iOS devices around for when I really miss some apps. And it seems a lot of people are on the same boat, looking at iOS apps as unitaskers that they'll chain and shoehorn into workflows that fit their needs, more than as "just works" magic tools.