Yet we keep using the a-10 to fight against non-modern air defenses over and over again. It has a use. If ukraine had them, would russia be able to shoot them all down? The answer should be yes, but russia should have waxed ukraine theoretically.
Russian AA is killing Ukrainian Migs very well when they're not careful. No one is flying over Ukraine very much because both sides have AA dominating all engagement altitudes.
I don't think you understand the kinds (and volumes) of SAM firepower a Soviet hangover can leave you with. Ukrainian skies are the most dangerous skies in the world right now, for both sides.
I wasn't trying to say that a10s should be used in Ukraine (because they'd be shot down). But a10s are still really useful in many other circumstances, most recently when fighting countries without air superiority. So if the us fights China, it doesn't seem like they'd be that useful because the us might not have air superiority and it won't be a tank war.