I think the "Didn't vote, don't complain" thing holds some weight even if yes voting does not create all change.
If you're complaining about something the Governor of your state has implemented, and you decided not to vote when the other candidate wouldn't have, you kinda wasted an opportunity to try to prevent it.
That being said, there are a lot of things that voting wouldn't stop and that's where that line could fail at. I don't think anyone with sense thinks the only way to change stuff is to vote but it does change some things based on who you vote in.
I agree with the part that says that voting isn't the only way to enact change. HOWEVER, I disagree that you should complain about the election results when you didn't even bother to exercise your right to vote. If you're not going to do your part to make sure that a candidate that you agree with gets put into office then why would you complain when other people get their way? After all, those people wanted a specific candidate in office and they made sure to do their part to make it happen. You didn't.
It probably took more time to come up with that argument and put it into almost-convincing words than it does to click a few buttons or fill in a few circles on a ballot.
Voting is important, but he is right that large scale systemic overhauls don't come via voting. The point of this message is to get people to realize that fundamental change can only be effected via large scale participation in government; voting is the most minimal activism ever, if even that. To paraphrase, no system of inequality, discrimination, etc. has ever been dismantled by only a vote.
I didn't vote on Brexit when I had the chance, so I have no right to complain. If you were unable to vote for various reasons is one thing, but being able to vote and choosing not relinquishes your right to complain about the results.