Even before the war, the practical cases for admitting Ukraine and Georgia to NATO were very weak, weaker even than for the Baltic states. Neither Georgia nor Ukraine have stable, pro-Western democratic governments. The Saakashvili regime has made strides beyond previous Georgian governments but has been reluctant to allow full freedom of the press and freedom of assembly. Moreover, Georgian control over its own territory (including areas not part of Abkhazia and South Ossetia) is often suspect.Overall, the admission of the various Eastern European states to NATO has been a positive development, regardless of whether or not Russia objected at the time. But there are diminishing returns to expansion of any organization, and I've long thought that NATO has pretty much hit its limit. It isn't just a neat club to join, after all, it's a mutual defense pact — and that's something worth taking seriously. We should make mutual defense commitments only to countries that are democratic, stable, likely to remain that way, and genuinely critical enough to Western interests that every member of the alliance — not just the U.S. — is willing to go to war over any of the others. Expand the alliance too much, and it loses its credibility. Just because Georgia and Ukraine are friends and allies doesn't automatically mean we should bring them into NATO.
In Ukraine, the presence of a substantial Russia population means that a shift in geopolitical orientation (away from NATO and toward Russia) is easily conceivable through democratic means. It hardly makes sense to allow Ukraine to join NATO in order to defend it from Russia, then watch Ukraine adopt a pro-Russian stance after the next election.
The Baltic republics represent the weakest cases for entry into NATO, but their applications were nevertheless much better than Georgia's. Each was more democratic than Georgia when negotiations for entry began, and each had maintained that democracy for over a decade prior to entry. Georgia shares a border with Turkey (a longtime NATO member), but the Baltic states are geographically much closer to the NATO core. While all three have substantial Russia minorities, none were likely to see the rise of a pro-Russian government, and none had outstanding territorial conflicts with Russia.