Russia already has NATO on its border, it doesn’t want Ukraine in NATO (and especially the EU) for Putin’s nationalistic narrative.
Maintaining client states means Russia isn’t total shit. Losing them would force a reevaluation of that conclusion.
The land border with the Baltics is small, and their westernisation a done deal.
Putin doesn't want Ukraine to go the same way. Ukraine's land border is vast, and Russia also wants continued access to a warm water port via Crimea.
So we agree there isn't a valid military concern here, NATO has border access and of course air and nuclear through other means.
Putin needs client states or he has to give up the image of restoring Russia's power. It's understandable Ukraine doesn't want to be involved.
True. Also, Putin sees Kiev as the first capital of Russia (Kievan Rus) and he wants to go back to days of Soviet Union. He openly says that he sees Ukrainians as part of the Russian nation. Acting like his intentions are reasonable and his ambitions modest is simply incorrect.