I feel like most ukrainians aren't fighting for democracy. They're kleptocracy is marginally better than the one in Russia, but not worth dying over. Their fighting either for nationalism and hatred of Russian imperialism that's oppressed them for centuries, or personal honor and fear of being called a coward by their wider social group.

In general nationalism and personal honor are the main reasons people will voluntarily sign up, outside of personal gain and mercenaries. In the west that nationalism gets tied up with ideas of democracy, but if a dictatorship took over the u.s. I doubt there'd be much of a difference in volunteers for the next war.