Another blanket response.
Introverts can be social, they can be very social. They are just not social in the same way extroverts are. Shy people may need to be coaxed out of their shell, but shy does not automatically mean introvert, and introvert does not automatically mean shy.
Added - introverts tend to be more social in small groups and one-to-one interactions, which may be a partial explanation for why we like being on this forum. Huge noise New Year's Eve parties are only fun in small doses (like once a year), posting on a calm, thoughtful forum is fun all the time.
Birth signs do have some value as information, since they are based on time of birth. So we can look at them as seasonal indicators - a summer baby has had a different environment than a winter baby - what seasons was the mother experiencing (cold/heat stress, amount of exercise, etc.), what was the weather like when baby was born, what weather was baby exposed to at different ages, etc. My DD and I were both summer babies, for example, and we were both old enough for long outings in the baby carriage in winter (well bundled up, of course). If she had been born in January I am not sure either of us would have been up to long walks in February ;-)