Practically all of that 20% was captured in the first six months of the war. Since then the Russians have been struggling. It has taken them 11 months to advance 50 km towards Pokvrosk in a front that is no more than 30 km wide. Most of the rest of the front has been stagnant. And even here there has been a slacking of the advance in the last few weeks. Yes, for over two years the gains have been minimal and at great cost.
If I occupied 20% of your home, some of it right next to your living room, would you see that as minimal?