Democracy and socialism are not opposites. Democracy and autocracy are respectively capitalism and socialism.
Given Vulcan discipline and their superior mental and bodily skills their economy is most likely more productive than Earth's.
Their suppression of emotions does not handicap them in the least, it merely leads to a rigid society (arranged marriage, all the other stupid, religious-like rituals) which is so rigid in order to prevent Vulcans from doubting the dogma of emotional suppression. The fear behind this orthodoxy is that lack of emotional suppression will initiate a "return to the savage ways".
I don't see what the suppression of emotions has to do with a rigid society or arranged marriage. That seems to be more connected to the way many Vulcans seem to be very Conservative, Orthodox, and tradition-bound. Kind of ironic for a "logical" society.
Vulcans suppress their strong emotions, that has become their way after the Surakian revolution. The folks who left Vulcan at this time found another way to deal with their emotions.
While Surak seems to have advocated pacifism and a suppression of nasty emotions his ideas have become a dogma over time. Vulcans fear the equivalent of liberalism because if everyone could do as he pleases some of them might choose to not suppress their emotions and "return to the savage ways". This dogma has probably been generalized over time, out of "don't question our principle of emotional suppression" became "don't question any Vulcan tradition", hence all these antiquated rituals with priests, arranged marriage and so on.
TFF, "Fusion" and Spock's evolution (TUC, Unification, ST09) show that these fears are only partially justified, that it is very well possible for individual Vulcan to "ease up".
As the whole is greater than the sum of its parts this does not necessarily imply that a more relaxed attitude to emotional suppression can also work on a the social level for the Vulcans.
This is the only potential explanation for Vulcan orthodoxy which stands, as you have pointed out, in sharp contrast to their official ideology I am aware of.