You might try a camera

I have a flatbed with slide adapter. VERY slow going, and not great quality. Had about 1500 slides to do, so I experimented with a camera and am very pleased. You may not agree, but here was my situation:
The slides were well organized in carousels. They were family photos from the late 60s to early 80s. Typical amateur snapshots.
I set up the projector with a nice big screen in a pitch dark room, and lined it up square to the screen. There is a little keystoning, but I aimed it as straight as possible, with the camera lens directly over the projector lens. Low speed, long exposure, no flash, tripod, auto-timer.
Once you get set up and work through a few, you can fly through them rather quickly. The slowest part was tilting the camera for the portrait/landscape orientation changes. Even that eventually became rather quick.
I did some touching up. Auto-correct for contrast, etc., which is easy if you image editor does batch processing; cropping/straightening if you want to make them pretty.

Good luck.