I disagree with this on a number of levels. Ideologically, I think this is very much China's fight. In The Narrative(tm), Ukraine is an exemplary democracy and bastion of civilization standing against the Asiatic horde. Not only is it disgustingly racist, it's a complete fabrication. Ukraine's government makes Russia's look squeaky clean and it's been perpetrating crimes against humanity with abandon in the Donbass for the last eight years. No matter how false and morally repugnant the narrative is, it's the prevailing narrative in the West - which means the "exemplary democracy" must fall, and China must be seen to have a hand in its fall. This will have a powerful demoralizing effect on the enemy.
Let's say some miracle occurs and Ukraine "wins" (however one defines that). The West will be galvanized and emboldened. It will see that if it stands united it can still shape the world in its favour and will look to continue its crusade. Who's the next target of that crusade, do you think? People develop gambling addictions by winning, not losing; that's why the West can't be allowed to win.
On a strategic level, let's imagine that China is waging a war in the Indo-Pacific to establish its predominance. How do you want Russia to think about this? Would you prefer that they think "China stood by us during our trying time, so we'll stand with them now" or "This is an Asian war. Why should Russia bruise itself over it?" This is a great opportunity to deepen the bonds between Russia and China, and those bonds will be needed in the years and decades to come.
