The screen being able to display a 1080p resolution (1920 x 1080) is a very different thing from your graphics processor being able to run TSW2 at a playable framerate at that resolution. My work laptop that I'm using right now has 1080p but it could no way play TSW2 in any way. In the same way, your car's speedometer might be able to read all the way up to 260km/h, but the car itself will never reach that speed without upgrades.

4k (3840 x 2860, four times as big as 1080p) is extremely demanding and only high end GPUs can run games smoothly at that resolution.