From quickly scanning Wikipedia articles, their governments seem to have a bizarre mixture of feudal and liberal elements. For example, the Venetian doge was styled similar to a monarch, but he was also an elected official and had increasingly diminished political power. They had a legislative body that was filled with oligarchs, but the oligarchs then conspired to make the legislative body de facto hereditary, turning themselves into a form of aristocracy. Overall, they feel like republics with feudal characteristics.