Why do the rotate map buttons instantly show the new orientation, like it was a 2D game?
We have 3D technology now, so why not to an animated (tweened) snap rotation that takes 0.5-1 second when you press the button?
I always get disoriented and lose track of where I was and what I was looking for when I use the rotate buttons.
Maybe I misinterpret something, but with the free camera option it rotates pretty smoothly for me. The 45° snapped rotation is weird, I agree.
If you don’t know how to change the option, go to “Options”, “Gameplay” → check “Free Camera”
Hope that helps … 
My free camera was already on, but I don’t know how to use it. I would have expected it to be the middle mouse button, but that merely zoomes out.
Note, I only use the mouse, no keyboard (which is difficult since some actions require Esc, and thus, a special mapping on an extra mouse button).
The only way I found was to rebind mouse buttons to the rotation (normally Q and E) in the options. But for that you need a mouse with more than the usual 3 buttons. Mine has 5, so I could use button 4 and 5 for that, but I stick with the keyboard, unfortunately there are no alternative key bindings.
My mouse can scroll to the left and right if I push the scroll wheel in those directions, maybe bind Q and E to those?