I wouldn’t touch this with a ten-foot...
OK, a serious question: if the Myceneans could get this far north, why not the Hittites, who were much closer?
The Hittites weren't around all that long, contrary to the conventional pseudochronology, and there were others parked in the way, lots of competition. The Assyrian Empire, which existed in some form for over a thousand years, was basically destroyed thanks to a confluence of the Babylonians, Medes, and Scythians, the latter two of whom occupied much of the area between Babylon and what is now the Ukraine.