Putin is stressed, look at the pictures where he met up with his officials to discuss the Kursk attacks. And Russia is a global player, they aren't a regional country like you make it seem.
Lol we could say the same thing about Russia capturing tiny ukie villages while suffering heavy losses
But it's not just border villages, there's literally a nuclear power plant in the area, they could capture it and shut down 1/3 of Russia's electricity, also use it as a bargaining chip in negotiations (same goes for the captured land). This isn't just some sabotage action, this is the largest land incursion on Russian soil since WW2
This will only fuck Russia even more, they can't afford to destroy their own infrastructure, and ''burn the food'' the russian troops barely get enough food in the first place. Don't forget what kay said about sanctions
And ukranians arent dumb they arent gonna march straight towards Moscow.
My last point: If it wasn't such a big deal then why did the russians evacuate 16k people from the area?