I’m not really sure this true. Russias strategy going back centuries has always swamped it’s enemies with a seemingly never ending supply of manpower. Most of the time if we are not talking 1st world adversary they win. Its been reported the Ukrainians are losing 800-1000 troops a day. Unless the Russians are losing 10000+ a day its impossible for them to retake the east and highly unlikely they can hold the west.
You don’t know about the FABs which changed everything and every single NATO fortified city has now fallen in a span of 4 months. Backmut fell earlier, but Russia has made it a point to crush every single one and they did between February and 7 May.