Russia has 7.3 million men between 20 and 30. So conscripting a million men is going to have a massive impact on the country. Especially since a lot of the eligable Russians have left Russia as soon as conscription was announced. Russia already has worker shortages due to that.
Then Russia is mostly using old Soviet weapons. This means the arsenal is going down. As long as Ukraines losses in equipment are replaced that looks pretty decent.
The big question is the politcal will to see this throu from the West. The Wests economy is much larger then that of Russia, so it can be financed with greater ease. However Ukraine has to deliver on destroying a lot of Russians.