The truth of the matter is that combined arms offensives are really hard, even for countries like the USA. It’s doubly hard to do it without air superiority, since the Russian air force has considerably more aircraft flying than the Ukrainian one. They also have incredible air defense. There’s also a massive defensive line in Zapporizhia, where the offensive is apparently happening.

Desert Storm was after a massive air campaign destroying logistics and communication, but the Russians have a whole year of learning to disburse their logistics, making it that much harder too