Traditionally I have run mostly homebrew adventures. I’ve used encounters taken from commercial adventures every once in a while. The Dragonlance campaign I’m running is the first I’ve really tried to run a module straight.
My players aren’t always going along with that idea but that’s ok. I’ve also added some content because I wanted a special event for the character with divine powers. I plan to do the same for the knight. Due to this I created Dulsi’s Dragonlance Addendum on DMs Guild.
For Spelljammer I found the process less satisfying. I had to tweak many individual encounters to match what I wanted. So running it requires looking at the adventure and looking my notes for things to override.
I have never used a campaign module as written. I don’t know that I could. I started with homebrew adventures, and that’s what my mind adapted to.
I get an idea of the adventure module in my head as I read it, and then I fill in the idea by myself. I often think over, adapt, expand and rewrite aspects of the idea, making it something I feel I could portray to my players. Then I use the original adventure as reference to fill in the gaps during gameplay. The end result is my version of the adventure, which is like the same image drawn by a different artist: recognisable, but different in obvious ways.
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.