The Soviet Union lost the Cold War and collapsed from within largely because they could not afford to keep up with the huge military spendings of USA and the collective Western forces.
In Ukraine, we are seeing the same pattern. Russia stands more or less alone, while most of the world stands with Ukraine. The Russian army was in a sorry state of neglect, corruption and disrepair before the attack on Ukraine, and over the course of a drawn-out conflict, something that Russia clearly did not expect, we have seen a gradual depletion of modern weapons like cruise missiles and smart bombs, causing an increased reliance on older, less effective weapons such as rocket artillery. On top of that, the Ukrainian resistance has caused substantial losses not only to Russian troops, but also to Russian equipment. Hundreds of Russian tanks have been destroyed, captured or abandoned by their crew after they simply broke down.
While Russia now has to resort to deep dives into their stockpiles of old and outdated equipment, some of which is not even in serviceable condition, Ukraine receives a substantial supply of modern weaponry from their allies in the EU and US. As the horrendous war crimes committed by Russia come into light, the support for Ukraine is increasing, and what few friends Russia had at the start of their failing campaign are withdrawing their support, even coming out against them.
Russia is now deploying desillusioned and weary troops using what basically constitutes Cold War era equipment against a modern, well equipped and highly motivated Ukrainian army. The war will not be an easy win for Ukraine, and it will be ugly, but Russia is losing.