Yeah, if Ukraine was going to join NATO anyway, it really should have in 2008 (or even in 2004, at the same at time as the Baltic states), while Russia was much weaker. But I think that Ukrainian internal politics may have prevented that, since it has always been divided into pro-Russian vs. pro-European factions.
But even if could join NATO, that still may not have been the wisest move. I remember reading an influential strategist (Zbigniew Brzezinski) who supported Ukraine's economic integration with Western Europe, but who didn't want it to join NATO. He wanted to end Western-Russian antagonism knowing that it forced Russia to turn to China.
If Russia is forced into an unsustainable arms race with the West, the fear is that Russia could fracture. The central Asian 'stans' would automatically turn to China; eastern Siberia (and its vast mineral wealth) would become a Chinese protectorate. There are worse things than a strong Russia.