The extra weaponry being supplied to Ukraine by the West is making a big difference. The new US-supplied artillery can fire 10 to 12 km further than the Russian equivalent, so you have the situation where the Ukrainians can sit and shell the Russians, but the Russians can't shoot back. And that's on top of the anti-tank and drone successes.
I think we're going to see some big advances by Ukraine in the next few weeks, but once they reach the areas that have been occupied for a while, they might hit problems. Crimea, for example, has been in Russian hands for 8 years. Whereas I can see that they would want it back, it's not going to be easy.