Comment by jwr
Relying on EXIF is a good thing. But if you limit yourself to ONLY using EXIF, you can't group images, make one image in a group the primary image, assign common metadata to the entire group, etc.
All turned out to be essential in my photo archives, especially as I started scanning old pictures. You get the front and back side of a photo, or you scan a large-format drawing in 16 scans and store them alongside the merged one, etc.
Aperture used to handle it pretty well, but Apple dropped it. I learned my lesson, and now I'll be doing things differently.
I solved the "one photo in multiple albums" EXIF problem by using Keywords. Each album is a Keyword.
But yes, there are some other limitations that would be much harder to solve. But it's a tradeoff I've decided to make - if I can't figure out an EXIF-based solution then I'm not going to invest time using it because it will likely be lost in 5-10 years.