The image on the bottom shows the percent of Ukraine, Russia has taken by year.
We can see in basically the last 3 years, overall Russia has lost ground. In fact, the Russian territory Ukraine took in Kursk is equal to all of the territory taken by Russia in the last 8 months.
Let's look at the cost in men/vehicles of Russia by year.
The number losses below are in order of 3rd year - 2nd year - 1st year
Artillery 13.6K - 7.6K - 2.4K
Tanks 3.6K - 3.2K - 3.7K
Amored Vehicles 8.7K - 5.8K - 6.6K
Vehicles 25.5K - 7.8K - 5.2K
Personnel - 459K - 262K - 147K
Other than Tanks, we can see each year it takes many multiples more equipment and men to make an insignificant change in territory gained. The reason why tanks isn't higher is that they are running out of tanks, so they are using Armored Vehicles/Regular Vehicles/Human waves as replacements.
In the first year, they had their professional army fighting. Many were lost when Ukraine had the manpower advantage and elite Russian companies were put in strategically poor situations.
In the second year, they had Wagner and prison conscripts.
In the third year, while they still have some PMCs, regular army, and prison conscripts, the bulk of their army is made of contract soldiers who are willing to fight for a signing bonus. They are running out of those soldiers.
They can always go to a draft, but that is something Putin hates to do in case he has domestic issues at home.
You can see why the waiting game is in Ukraine's favor, especially as they are taking more refineries off line, have air superiority in via drones, and Europe is starting to board some of Russia's shadow oil tanker fleet.