While it's nice to think that airlines can just rely on regulators to tell them which flight paths might be unsafe, the reality is that there's no international regulatory agency governing acceptable flight paths. There's a regulatory agency for every country and while one country might have stringent safety measures, another might not.

In such an environment it seems naive for an airlines to not include the safety of the flight path in their calculations. If all civilian flights below 32K feet are forbidden by the Ukrainian authorities, that doesn't automatically mean that flying just 1000 feet above would be safe. Also while other airlines are guilty of flying over war zones too, that doesn't mean Malaysian airlines is not.