Russia may not be able to deploy its airforce freely over Ukraine, however they have a significant amount of artillery and firepower. Artillery/rockets and kamikaze/strike drones, especially when directed by surveillance drones can get the job done imo. The biggest issue hampering the Russian military right now is their lack of manpower. In Ukraine they are outnumbered atleast 3 to 1, in some instances 5 to 1 or more. An army on the offensive is supposed to outnumber the enemy 3 to 1 atleast, the Russians, despite being outnumbered have shown that they can even conduct successful offensives, which proves that their military is not incompetent or incapable.
Remember this is a high intensity conflict. Both sides are incurring losses, but even in the Kharkiv offensive, Ukraine lost 5 soldiers for every 1 Russian soldier killed. Currently Ukraine is on the 9th round of conscription. Increasingly we see women and elderly men joining the ranks. Ukraine's methods are simply not sustainable. They don't have an endless supply of men and weapons. In terms of weaponry and supplies, Ukraine is 100% reliant on the west now.
In the long run, Russia is preserving their military as much as possible. Sure Russia has lost a significant amount of men and equipment, but it's simply nothing compared to Ukraine's losses. People don't realize this but since the Kharkiv offensive, Ukraine never stopped pushing forward. Since then, this entire time they have been throwing everything they have at Russia, especially because the weather is becoming increasingly cold and wet.
Ukraine has at most another month, if that, to take territory. This will not be an easy winter for the Ukrainians and they'll be lucky if Russia doesn't launch a major offensive during the winter. In any case, when the Russians deploy their mobilized personnel, Ukraine will be in a very precarious situation. Just in the Kherson region, Ukraine in the last month has sustained thousands of casualties and hundreds of armored vehicles and tanks destroyed. Look I'm not saying that the exchange is completely one sided, but in the long run, Ukraine's methods are unsustainable and in a total war, Ukraine can't win against Russia.
Think about it Ukraine is on the 9th round of mobilization and half of their vital infrastructure has been destroyed. Russia is on the first round of a partial mobilization and already the Ukrainians are shaking in their boots. They claim to be shooting down 80% of Iranian drones, yet realistically we hear about Shahed strikes every day or other day and if Ukraine is so successful then why do they keep begging the west and Israel specifically for air defenses. Also why is the west making such a ruckus over Iranian drones if they're so ineffective. Dozens of nations are supporting Ukraine. You have one nation helping out Russia and the western nations are having a panic attack.