The problem is the political implications... for one, it would send a signal to China that a land-grab against Taiwan will yield a bit of trouble but nothing too serious. That's the worst case and I seriously hope that that alone (and the economic devastation associated with TSMC blowing up their fabs to prevent them from falling into Chinese hands) is enough to keep the support going.
The other factor is that it might lead to a complete fracture of the NATO - Finland, the Baltic nations and Poland will not accept any kind of Russian success out of that war. They're all no big economic players in the EU/NATO, but a major internal dissatisfaction in NATO may entice other players in the world to play rough again as well, not just China.
Ukraine gave up their nuclear weapons and long strike weapons in exchange for a promise to not be invaded.
After Russia broke that promise who would ever make that same deal again?.
That is assuming the Russians eventually pull out of Ukraine, are completely beaten militarily and their assets will be used to fund Ukrainian reconstruction, and it assumes that China does not increase tensions with Taiwan or, heaven forbid, actually invade.
Should the war drag on, the situation will grow completely unpredictable - eventually, governments (no matter their political orientation or prior campaign promises) will have to raise taxes to pay for Ukraine aid and especially new arms projects, which means price hikes for the masses as companies will just pass through tax increases instead of accepting lower dividends for the capitalist owner class.
> but you cannot predict how millions of people will react to suddenly not being able to afford stuff.
IMO: Riots are inevitable IMO unless politicians invest money into at least filling the gaps for the lowest rungs of the societal ladder, the French are blazing the trail here - and it's only a matter of time until at least the UK population has enough of empty supermarket shelves. In the US, it depends if Biden will be able to secure a second term.