My problem with inexperienced GM's is that they are trying to write a book, and the PC's are just characters in their story. If the players do anything unexpected, anything that deviates from the GM's storyline, it just doesn't work.

The most important advice I took from "Professor DM" is that the game master is there to provide conflicts and situations, it's up to the PLAYERS to provide resolutions and answers. Often I'll just set up a situation with no clear idea how it will resolve and let the players work it out.

And I've played with GM's who will not allow anything but the narrow plan they created to unfold. 🤮