My thoughts are cost, and the aspect ratio of the posters mean there's a lot of cutting off of the sides of the posters.
Have you ever considered handing off the frame to a wood shop? I appreciate not everyone can build something but one could build a pretty nice frame,
for a $150 investment in a wood chop saw, and a biscuit miter (and those tools could be leveraged over other projects).
I expect the value might be in the software, but a DIY digital movie poster frame can be a pretty simple and fairly inexpensive project. My simple KISS version of this,
could be a cheap Black Friday 1080P hdtv, a usb jump drive, a hdtv skim wall mount, and a piece of plywood.
The real time suck in all of this, is actually the graphic work poster-wise. A 1000 posters is a pretty extensive collection, but 4K is likely putting a potential limit of posters, if
one wants to avoid upscaling.
As for fit and finish, I actually plan to beat on mine, to distress it a bit. Going for a moody industrial look.