Not being defeatist as much as being realistic
When putin is pushed to use a tactical nuke what do you do then?
Do you think he will declare defeat before he plays that card?
Eagler
Being realistic means looking at the overall situation based on facts while cutting through the vast volumes of propaganda from all directions. That is tough to do.
Tossing nukes is one of the "win" scenarios for Putin. So far, he has decided that the downsides are not worth the try. It really is hard to say if he will get to that point. No one knows if he is willing to go that path some time in the future. So, saying that Putin will certainly prevail based on that possibility does not mean UA can't reach a position of "winning" no matter what they do.
In reality, neither side can "win" in the sense of getting more out of the process than what it costs them. They are both certainly going to pay a very heavy price to get where ever they end up. Putin had a chance early on with the initial push to decapitate UA's government but it failed badly for a number of reasons, primarily Russian incompetence. Now both sides are stuck paying a brutal price hoping that continuing will yield better results than their current situation.