With all the bold talk on 300K more soldiers do not matter, if they are in trenches and not attacking, they make it much harder to recapture territory. In both Kherson and the fortified areas of Donbas (Lyman, etc), the advance by Ukraine stalled out. Progress is being made, but if gets harder and harder to take territory and losses to do so goes up as well.
Fall rains and then winter will stall it more which gives more time for Russia to dig in.
Maybe it will all break through, but time means harder and harder to get the Russians out.