I'm not saying its unplayable for everyone, I am saying it is completely unplayable for me. None of the click spots align at 4k resolutions for me. From the main menu I have to spend several minutes finding a click spot which appears to be in the upper left say about 1920 x 1080 pixels of my 3840 x 2160 resolution. The click spots are significantly smaller as well so very difficult to find and select something. So with the F-18 background image, the module icons displayed at the bottom highlight when my mouse is on the horizontal plane with the middle of the F-18 fuselage from behind the jet exhaust to about the middle of the right wing. The "Exit" button highlights when hovering just above the plane number on the right wing.
Getting to and adjusting settings is extremely difficult. I've also tried the mission editor and everything is off there as well. What I haven't tried is loading an actual mission to see if the click spots are also off in cockpit. I haven't bothered yet because it would just be an exercise in frustration.
I stand by what I stated, it is unplayable right now for me and it sounds like for others as well.
****Update****
Ok, I decided to do a couple of test to give additional information. First off, I did go ahead and test click-spots in cockpit and found that they do work as they should. If however you press ESC to access the menu to adjust controls, view the briefing etc., the menu that pops up will have the clickspot offset issue.
Next, i renamed my options.lua file so it would build a new one on startup. First I only changed the resolution option to set my 4k resolution. After the restart, clickspots were good so next I enabled the Scale GUI option (using Win10 175% scaling option). After a restart, the click spot offset issue comes back. I tried with Full Screen both on and off and no difference. Hopefully somebody can figure this one out soon.