The Russians made a remarkable improvement in their tactic and in their drone arsenal, In this sens, they learned very well from the Ukrainians. They have accelerated arms production and upgraded soviet era bombs. Even more remarkably, the morale and motivation of the Russian soldiers have improved somewhat despite heavy losses.
This is because the Russians see as a victory the failure of the Ukrainian counter-offensive and perhaps because there are more troops sent to the front. The more they are, the stronger they feel.
Russia has currently >617K regular Russian army troops inside Ukraine + an undisclosed amount of non regular troops + the entire logistic inside Russia. (617K is the number given by Putin himself during his press conference). This compares with the 190K troops at the beginning of the Special Military Operation. More than 3x more.
Adding those who already left the front line either because they were too severely wounded to return or because they are dead, the total contingent was about 900K. When you know that you need 3 persons behind the war zone for each soldier on the battelfield, it can be concluded that the entire Russian army is working for the war in Ukraine.
So not only the Ukrainians lack just about everything, including men willing to fight, while Russia have every of these things in greater number. This is because when Putin saw that he was about to be defeated completely, he ordered maximum effort at every level of the Russian defence aparatus.
So it's not just that the Russian line of defence was well prepared, it's also because the Russians have increased their forces by threefold and their efficiency.
The Ukrainian army improved also, but the numbers don't match the clash of the titans happening in south east Ukraine.. And they still lack fighter jets, bombers and long range missiles.
Their only hope is that they receive them next spring. They are expected by May or June next year if everything goes well. if Trump wants to stop military aid to Ukraine, they better get them before he is re-elected.
Their second hope is that the Russian front line collapse suddenly after sustaining too many losses. There should be a point where Russians will decide that they don;t want to be killed. For the moment they don't have that feeling. Quite the opposite. But the trend could reverse one day when no one expects it, if Ukrainians can keep up the tempo.