Ukrainian army was at its peak when the war started. It's been significantly reduced in capacity since, and the weapons that the west sends come nowhere close to replacing what was lost. If Ukraine couldn't win with its original force, why would anybody expect it to win with a hodgepodge of western weapons and a decimated army. Even western publications are starting to grudgingly accept that there is no path towards Ukraine winning this war.
What's actually happening is that Ukraine continues to lose territory. The longer this war goes on the more territory Ukraine will lose, and end up in an increasingly worse bargaining position.