If they manage to capture the coast including Odessa and the Donbass, they will have recovered a large chunk of the Russian speaking population lost after the dissolution of the Soviet Union and add a lot of industrial capacity. Long term this would benefit Russia, Ukraine would be reduced to a rump state.

But yeah the pre-2014 situation would be vastly better for all sides involved. Ukraine could have taken the Belarussian or Khazak trajectory.