That is my experience too, I had thought a dxf file was like a .fzz file or a .brd file for eagle, but it appears to be closer to a svg, just the image with no interconnections or net which means it isn’t possible to make a part out of it very likely. To redo the boards in Fritzing would mean being able to find all the parts in use (and I don’t know what parts are in use.) I haven’t looked at Autocad in 30 or 40 years, but does it not have a board output format of some kind (other then dxf?) I would expect it to be a full EDA package by now, but perhaps not.
Peter