A battle lost doesn't mean the war is lost.
Only need to look at Britain beginning of WW2, Disastrous retreat to Dunkirk and almost the entire army captured, but rebuilt over next 3 years to defeat the Germans.
IMO some posters read far too much into too little.
One has to look at which side can last the distance in a long war. If the NATO countries currently sending arms decide the cost is too high, and stop- what then for Ukraine?
If the current financial situation deteriorates, will taxpayers continue to accept spending billions to support a war they are not even fighting in?