[...] is a provocation worthy of military invasion?

See, that's an entirely different statement. Threatening to join Russia's geopolitical rival's military alliance while bordering Russia, is provocation. The acts in Donbas since 2014 are provocation. Is it "worthy of military invasion"? I don't believe so. The proto-fascist Russian government is clearly not acting entirely out of pure will and self defense, and I'll be the last to defend it since I have loved ones directly suffering under that government. But it's important to frame things correctly, and yes, threatening to join NATO while bordering Russia is a huge provocation.

Particularly, NATO has no history of defensiveness (as far as I know it has never intervened for the defensive purposes it's supposed to uphold), but it has a history of offensiveness. Yugoslavia and Libya can both attest to that, and extra-officially (technically not NATO interventions even if many NATO members participated one way or another), countries such as Iraq can also attest. The case of Iraq is a perfect example of what unprovoked invasion in modern times is, and we are still forced to see libs fall heads over heels for a fucking Dick Satan Cheney endorsement to Kamala "most lethal army in the world" Harris.

So, yes, when a country bordering you chooses to join a historically aggressive military alliance that openly challenges you, that's huge provocation. And it's important to state so when we talk about the war in Ukraine.