The new Photos app is still annoying to use.
Take this picture for example, where two red lines go from corner to corner.
If you open that in the Photos app, the menu covers a good portion of the upper half. I don't understand the thought process behind the menu covering part of the picture itself. The menu shoult not cover the canvas!
In the old Photos Viewer you also had a button that either scaled the picture to 100 % or to fit the screen. There was also a zoom slider. All of which was removed in the new photos app. Oh, and you could use the mouse wheel to zoom. But apparently, mouse wheel's aren't a thing any more.
I don't know what they were thinking, but it must have been something along the lines of "Hey, let's take the Photo Viewer and make it really, really frustrating to use!"