No "likely" about it, we could hurl nukes at it no problem. It's more what that'll set off that we're concerned about. There's no real calculation or dilemma here, aside from the obvious problem established since the end of World War 2.
Power level time, I have several wonderful Ukrainian friends. One of them is currently trapped in Kyiv as we speak. She's not scared, she's defiant and angry, and agree with her or disagree with her, her courage is inspirational and I wish there was more I could do help her. This has been enormously difficult for me to write about and follow as a result.
That being said, I still acknowledge that I'm not willing to risk nuclear war over Ukraine, and I don't think anybody suggesting it understands the full implications of what they're asking for. Sending over support, economic sanctions, helping refugees, sure, within reason. A no-fly zone or declaration of war? No. It's good to want to help, but that'll just lead to Ukraine being destroyed alongside the rest of us.