The supremacy that Russia has in Ukraine is of course not like the Americans had in Iraq because the west has armed and continues to arm Ukraine to the teeth, so whatever the Russians destroy will reappear, they have countless stingers, they got anti-aircraft systems from Britain and Germany, but the bigger problem for the Russians is the length of the front, especially when you take into account that the Ukrainian units are managed by NATO, which has all the data from satellites about where the Russians are, which enables such attacks on weakly defended parts of the front. The length of the front was also a problem for the USSR when it had over 5 million soldiers, and how will it not be for the Russians with 150k.
Russia is fighting against Ukraine, not the world.
Only the cannon fodder is Ukrainian, everything else that is important for the war is the NATO pact.
Well, the only thing that is not NATO is the soldiers themselves, everything else is. Intelligence, command & control, surveillance, weapons, equipment, ammunition, food, pay for the soldiers. It should also be added that apparently a large number of active NATO soldiers "on vacation" are working in Ukraine, training, analyzing data, managing complex NATO systems, probably there are also some on the front line where they pretend to be volunteers, there were a lot of videos where "Ukrainian" soldiers talk to each other in English which is quite unusual. That is why it is a priority for the Russians to hit Europe economically with a sledgehammer, to cause everything to fall apart, to cause mass protests, riots, ideally civil wars, because then Ukrainian logistics, equipment and financing will disappear.