My favorite DMing style is what I like to call “train line DMing.” The train goes to all the stops but you can do whatever you want at them.
There is a plot, no crazier than any purchased campaign, but it’s structure consists of a chain of open-ended* scenarios. Its a contract: the players are willing to follow the general and well telegraphed line of plot hooks and in return they do whatever they want in the scenarios and I do my best to incorporate their interests and backstories.
And like all contracts it starts with explaining that and seeing who is interested. Example: “I want to run a short campaign where you explore X looking for Y. Be whoever you want, except one key part of your character is they want to find Y.” Then we do it if people want.
*Open-ended here means “no right/pre-planned answer” not “no ending to lead to the next part.” For example, city A has a cult to deal with and the leader has a letter pointing to city B. Whether they kill the leader, join the cult, plan an economic take down to render the cultists penniless and impotent, or something weirder, they get the letter.
I’m running my first module campaign ever after being in DnD since my teens. The idea used to seem so foreign to me, but trying it I find that it works well as inspiration. I end up adding a lot and chopping out huge pieces and doing substitutions.
Honestly, I think that’s all modules are good for. Maybe older ones were higher quality, but the one I’m using is mostly fluff and vagaries. Suits me fine though, I know how to tune an encounter, but I’ve burnt through a lot of my major campaign plots already. As this one goes and characters get more involved I may discard the thing altogether.