Dungeons and Dragons

Hmmm, I guess I never used boxed sets, but I kind of assumed they gave interaction ideas / details to get the party started so to say. Honestly, if it were me I'd suggest thinking of DMing like collaboratively writing a choose your own adventure story. You sketch out / write some of it in advance, and each session go through one or more of the branching story and then you know where to continue for the next session.

If you're decent, you can easily handle players going off on different paths with some gentle adjustments to the world to get them back on track. If you're good, you can extemporaneously create these new paths and goals to some extent and let the players guide the story.

I think the important part is you need to create and guide a story somehow. Just having an open world with a list of things to potentially do is like a video game, and tends to (in my limited experience playing in this sort of game) lead to boredom in the players. Especially if the DM doesn't know how to do roleplaying vignettes or what and where they fit. Every trip through a town on the way to somewhere else doesn't need a full session of roleplaying the tavern and shops (unless the players angle that way). Every long rest doesn't need to take an hour of play time to work out 3 watches, 3 sets of players standing watch "talking" about ??? (when the players are like, I have nothing to say really), overland travel can just be quick travel if nothing but a random encounter might happen.