While I would agree that the statement overlooks several periods of breakaway states, civil wars, and foreign occupations, I am afraid you misunderstand the importance of the Qin dynasty. It lasted for 15 years, not 5 and it is the immediate predecessor of the long-lasting Han dynasty (206 BC–220 AD). It served as the template which the Han partly emulated and every other dynasty emulated the Han. Just about any Chinese state can trace its lineage to the Qin empire.