US and UK officials reportedly believe the offensive is going poorly because Kiev has split its forces
I am no military strategist but concentrating all your forces to achieve and advance in one region would sort of leave your forces open to being hammered by enemy air and artillery superiority and lead to the enemy perhaps thinking while you are pushing there they can push somewhere else and crush your lines of defence leading you to have to stop your counter offensive and go on the defensive.
The Ukraine cannot afford to move its forces around a lot because that takes fuel and will be spotted and punished by their enemy.
But why expect any common sense on Kievs side... if they had that the Minsk agreements could have sorted everything out with little to no bloodshed for either side.
What Kiev now needs to realise is that the enormous amount of blood Kiev has lost means nothing to its so called western allies and all they care about is that it was a chance to destabilise Putin and damage Russia. They failed in both directions, but that wont bring those Ukrainian men back to life... nothing will.
Kiev continuing to fight means more territory will be lost and the final terms will be more harsh... ask the Fins about terms with Stalin, the terms were harder after they killed huge numbers of Soviet soldiers and lost anyway.