It's the same problem I found on a colleague's laptop (one of the 4k touch screen).
at native resolution (of course!) icons are microscopic as well as texts.
constipation 3800*2100 pixels on a schemo 15" means a density Physical physics stratospheric, with the result that a large icon the number of pixels brought to video result physically A pinhead!
and result physically small all elements related to a fixed size of the program (e.g. menu, command line etc)
I tried to increase the size of icons, menu texts, windows appearance, but without result.
increasing the size of the characters even happened to me a small half with the menus and the writings.
I believe that autocad, in representing icons, menus etc, is based on pixel size and not as a percentage of the available screen area, problem that I do not think I have identified in office for example.
The only solution I found was to lower the screen resolution.
especially for a 15" screen I don't think going beyond 1680x1050 is good at visual level.
a bad solution I know, but the only one with simildecenti results at the visualization level.
the use of ribbons as tristan says could lead to some visual improvement of the icons, but does not solve the other problems (texts of menus, context menus etc) that are almost invisible.