From what I understand, the forces pushed back were not Russian, but allied forces and national guard forces...not exactly cream of the crop and they were defending unimportant areas where the pulling back was militarily smart as the areas were essentially disposable.
But, hey, good press right.
Kherson, Mariupol, Luhansk and most of Donetsk is still controlled by Russia and Russian allied forces.
Maybe it’s true about the troop quality, but it’s also irrelevant.
In May of 1940 Germany’s best Panzer divisions blew through the hinge of the Allied advance into Belgium which was manned by second line French reserve divisions (with severe command and control problems).
Obviously better quality troops would have stood longer and cost the Germans time and casualties.
However they were not there, and the Germans were able to get in the rear of the allied lines, cut supply routes and force the retreat to the Channel.
The Russian problem is that those second line troops folded like a cheap suit and have now exposed the right flank of the Russian line to attack. The have also allowed the Ukrainians to cut multiple rail links that were the primary supply lines for the Russian forces further South.
In war, logistics is everything. At best the Russians are going to have to detour supplies further East in Russia, at worst they won’t be able to do it and the forces in Ukraine may run low on food, fuel, and ammunition.