We are not talking about ancient times, we are taking about the last 800-1000 years, Kosovo was inhabited by Serbians, not Albanians.
As far as I am aware, Russia is not Serbia’s greatest ally, Serbia it working with Russia, China and the US.
I really don’t think the EU carrot will work, injustice is injustice, and it’s very difficult for an entire population to accept such injustice.
Sooner or later, the geopolitical situation will changed American politicians might not be as interested in supporting a criminal state whose PM is … well … see for your self
https://www.theguardian.com/world/2010/dec/14/kosovo-prime-minister-llike-mafia-boss
America might not even be the dominating superpower, things change.
I would not be to sure in Kosovo’s independence 40-50 years in to the future, Serbia has all the time in the world.