Ukraine has managed to do a lot in this war: they have repelled Russia’s attack on Kyiv, despite expectations and even pulled of two succesful counteroffensives. (I am talking about Charkiw and Kherson.) I know Ukraine is in a bad spot but that doesn’t mean that it’s over for them.
If they don’t want to negotiate and would rather fight, then why should we tell them they shouldn’t and instead should negotiate with the agressor? And why should we believe that Russia won’t violate such a deal? Their track-record isn’t great in this regard.
Wikipedia says that the Ukrainian armed forces consists of 1000000 armed personell. Compared to Russia’s 1320000. I don’t know the relevancy of this, but hey, I answered your question, now you answer mine.