Unfortunately the groundwork was laid down in the fall of the Russian Empire, and Soviet map-drawing. For example current-day Ukraine was essentially created by Lenin (even though they'd like to pretend otherwise). Eastern Belarus for example was administratively reassigned to the BSSR from the RSFSR in the 1920s because the BSSR was just too small. And western Belarus was just taken from Poland (like western Ukraine from Poland and Romania).
It's not dissimilar to the Azeri-Armenian conflict.
This is only half-true. Russia is definitely more discriminate in their use of violence then either the regime or the US-backed rebels. And they've made a significant effort to improve their ability to strike targets accurately. Granted, this is done for military reasons far more so then because they care about collateral damage, but nonetheless when you're backing groups that use hell-cannons in dense urban areas, it's hard to criticize anyone else.
They have a plan, and they're following through on it. The US needs to get their head out of their ass, and figure out how they intend to proceed. Because so far it hasn't been working out too well.