I'm fairly sure the going rate for not voting here is $50 or 'religious objections'. Society seems to say the answer to the OP question is 'yes'.
Whether that counts as legitimating the system is a very interesting question in post-Australia Act Australia. The Constitution derived its legitimacy from being an Act of UK Parliament, yet UK Acts are no longer applicable in Australia. So the only thing that makes it binding is supposedly popular sovereignty. Yet when it was originally voted on, women were only allowed to vote in South Australia, and of the remaining part of the population that could vote, only about 40% did, and a sizeable portion of them voted 'no'. So if the Constitution is to have any sort of continuing legitimacy, the basis of its popular sovereignty must be the present. Half the population aren't even aware that Australia has a constitution, and the rest have never had a chance to vote on it; acquiescence may amount to contractual acceptance, but that can hardly be a strong basis for a social contract. Now, if people are forced to vote in elections legitimising the system, are there any grounds on which it can be said that the Constitution and the system it enacts are popularly and voluntarily accepted? If you're forcing people to legitimise the system, it's not longer a true form of legitimisation. If that's the case, where does such popular legitimacy of the system come from?