These were very linear too though. Sure: some like Monkey Island had a map that gave you the illusion of having a whole world to explore, but there still was a fixed sequence of events that couldn't be broken.

None of the decisions you made had any effect for the future or could just flat-out prevent you from finishing the game. Some (Sierra) called that a feature, others (Lucas Arts) a bug.

Maniac Mansion 1 and The Fate of Atlantis are the only two Lucas Arts games that provided a little bit of nonlinearity. Maniac Mansion with its different ways to solve the game based on character selection and Indiana Jones with its selection of one of three quite different paths through the game.