Russia is claiming to fight NATO, but NATO hasn't even shown up yet, but Russia is struggling. If NATO were to go to war with Russia, there would be very little that Russia could do. The one thing they might be able to do is the reason NATO has been holding back.
As far as NATO showing up, they have. To the tune of over 300 billion Euros. I'm not sure how you can claim Russia is not fighting NATO. Zelenskyy is constantly requesting more and more funds and weaponry from the west, because without it, the Ukrainian side would not be able to put up the resistance that they have been.
And yes, Russia has taken some towns, but so has Ukraine. Ukraine just took Lyman back (again) as well as a bunch of land north of Lyman, undoing recent Russian advances there. It's the same story in many places: Russia spends a year making some small gains and extreme cost, and then Ukraine takes most of it back again.
It's a stalemate. There hasn't been any significant progress from either side in years. And what Russian progress there is, comes at a steep cost in lives, whereas Ukraine recently took some ground with nothing but drones.