I think the problem is that FTM2017 (like most other apps) is not DPI-aware. Modern high-resolution screens are great with photos and videos, but as David says, existing programs may end up with tiny unusable text and icons. Windows has facilities to try and resolve this, by scaling up the user interface automatically, but it's never entirely satisfactory - true-type text can be scaled and still remain sharp and crisp, but other fonts and aspects of the interface may either be the wrong size or look pixelated or blurred. Windows 10 has improved things further by allowing custom DPI control for each application, but it's still not perfect, and FTM in particular doesn't work well with some of these settings, and the "large fonts" option doesn't work at all on my DELL XPS 15 4K screen.
I think the only "guaranteed correct" alternatives are:
1) set the Windows scaling to 100%, and reduce the native screen resolution until everything is comfortably sized. That way everything works exactly as it was designed, and Windows' and app's text and icons etc. are large enough to use. The disadvantage of course is that you effectively have a lower resolution screen, so EVERYTHING is less sharp including photos and videos.
2) set the Windows scaling to 100% but keep the full screen resolution . While everything still works correctly, most programs and Windows itself will probably be far too tiny to be usable except with a magnifying glass!
3) the ideal solution is to keep the full screen resolution, set Windows scaling to whatever is comfortable/recommended, and for the developers to make all apps fully DPI-aware, so they declare themselves as such to the operating system and scale text, icons, etc. accordingly themselves, so they're the right size to be usable but still take advantage of the higher resolution and are fully sharp.
Unfortunately, as I know from my own experience, making an app fully DPI-aware is not at all easy, especially if it's an older program written using the Windows Presentation Framework (WPF), because it would need to be more-or-less completely re-written to use the Universal Windows Platform (UWP). I doubt that MacKiev will have done that with FTM :-(