1- The Qur’an is a clear guide when its conditions are observed. In chapter 3 verse 7 the Qur’an makes it very clear that there are ambiguous verses (for the purpose of trying people). If we follow the Prophet’s teachings and his family (the infallible Ahlulbayt), then yes the teachings of Islam are clear.
2- The Qur’an is clear to those who are qualified and and have proper knowledge of it. The Qur’an doesn’t say its verses are clear to everyone. It’s clear to the Prophet, the Imams, and those righteous Muslims who follow the Prophet and his family.
3- People can have different interpretations about simple and clear ideas. A holy scripture can say that God is one (that is very clear and simple), yet later people can have different interpretations (like Christians did with the trinity). People are motivated by their interests, their agendas and their politics, so it’s a given they’ll have different understandings of the Qur’an. But God is trying us and if we are sincere, we can have proper access to the knowledge of the Qur’an.