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.
All the expert opinions I've seen have reduced the situation in the east to a stalemate and possible Ukrainian regains in the south. Also, with how much I hear about Ukrainians being very disorganized at the start and with the further lack of any weapons apart from their own, it's odd to claim the Ukrainian army was at its peak. The Russians seemed to have simply failed miserably trying to take over the entire country quickly.
How much of territories Ukrain returned back to its control? Ukrain has a few tactical wins, like sinking down russian ship(s) and repell Russians from an island. But what are strategical gains since April?
From what I've seen, apart from Snake Island, they've made small gains at the very edges of the battle line but lost a City at the heart of the eastern battle. From what I've read, they're trying to form a bigger counteroffensive right now and have been urging Ukrainians to evacuate from occupied territories before the real battles commence as it'll get ugly. They're also getting another big batch of tanks from Poland.
Tanks are useless if you don't have air superiority. They will just get blown up. Same with artillery. You can't go on the offensive without controlling the skies.
Ukraine's only real advantage is the Bayraktar drone.