So instead of spending money to make the life of the citizens better, Russia wastes uncounted billions on a senseless war in Ukraine.

There are absolutely no any need in spending more money on infrastructure. There are more than enough money and resources to make everything perfect. Problem is purely in the corruption and incompetence of bureaucrats.

As for Ukraine, you could easily find out the state of ex-USSR infrastructure in Ukraine, Nothing was build, repaired or replaced at all since USSR fall, even in large towns like Kiev or Kharkov. It really makes people of new Russian regions wonder "fuck, we didn't know that it could be that way!" and "why didn't we join Russia much earlier?"