Venezuela is a dictatorship, not because Chavez wasn't elected, but because once elected, he put his finger more and more on the scales of the elections. He arrested opposition leaders so that they couldn't run effective campaigns. When Chavez died and Maduro came to power, he did more of the same, destroying the independence of the judiciary, and shutting down the opposition legislature.

Venezuela is a dictatorship whether or not Guaido won the last election. It's a dictatorship because the government took enough steps that it was impossible for anyone but Maduro to win.