It's that these programs have a UI design that seems, like a rebellious and none-too-bright teen, intent on breaking every convention. Options and views that come and go, ghostly and elusive sidebars. You want the 'collections' view in Photos, you have to press a back button from 'moments'. Seriously. What's a fucking 'moment' anyway and what do they have to do with with 'collections'? If you want a timeline, why not years < months < weeks < days? Uh?
And that they lose random features. Not all cameras have GPS and it's useful to know where a picture was taken. In ten years time I probably won't know where I was on 17 April 2015. In about five months time, I won't remember. I shouldn't have to play of a game isn't that the building in... Before you could select a pile of pictures, click 'get info' and add a place. Job done. It doesn't seem exactly an edge use case. It's information that it automatically retains for photos with the location added by the camera, though again not editable. Same for 'faces' which now clunks. Again, I'd like to be able to tag pictures and pull up, say, all the pictures I've taken in Hong Kong, or those that feature the delightful Cohort of Ms Frangipani.
The quest for reducing functionality to match that on a tablet continues. I blame Finestre, the Demon of Such Things. She had to trump skeuomorphism, which while inspired, hah had its day. She really does outdo herself. I think her performance review must be coming up.