I've been saying this for a while now but the reason for the stalemate is because both sides are suffering from inadequate combined arms capabilities when they advance, resulting in massive losses when each respective side tries to advance. Although they each have their strengths - the Russians with numbers, and the Ukrainians with better training and Western intelligence and support - neither side has managed to deploy effective air cover when they advance. This is amply demonstrated when both sides defend against the other's advances, but it's more damning for the Russians than the Ukrainians given their on-paper air force, but lack of training and poor tactics means their on-paper capability is just that, on paper. The West either needs to equip the Ukrainians with adequate air assets to provide cover (I think the A-10 and/or Cobras would actually be a better option than the Viper), or provide better intelligence for their advances, otherwise the Ukrainians are unlikely to make much headway before the onset of winter.