I'm not "enlightened", and you can draw your own conclusions. But they don't have to annex Ukraine, they can just mess it up and cripple its military. At the least, Putin's stated aim is "demilitarization" of Ukraine. As for the comparison with the Baltic states, I would note that this entire situation evolved over decades. Perhaps Russia would have more strongly opposed NATO membership for the Baltics had it been in a more powerful position when that was happening. Perhaps they thought that NATO-expansion would stop there. A lot has happened in the past 3 decades and some patterns are much more clear now than they were back then. One that Putin has repeatedly pointed to is that the USA is continuously supporting overthrow of governments that it doesn't like, even in the case of democratically-elected Yanukovich in Ukraine. Maybe Putin is paranoid to think the same can happen in Russia, maybe not. But I think in his view, maintaining the nuclear deterrent with the West is an existential concern, like it had been for the USSR. Having NATO missiles and bases in Ukraine is clearly a step in the wrong direction for that concern. I'm not saying that this justifies war or that Putin is right. I just think that Putin perceives himself as a cornered rat, and that from this perspective his actions make a lot more sense than just seeing him as deranged or a power-hungry demagogue. This perspective is laid out more fully in this talk by John Mearsheimer if you're interested: https://www.youtube.com/watch?v=JrMiSQAGOS4&t=120s

This is obviously a very sensitive topic at this time, and I hesitate even to post this comment. But I think everyone should be free to draw their own conclusions.