How to create pre-written adventures

Hi, everyone, thank you for your time.

There is a ton of info on how to run modules or steal ideas and encounters from them. However, I am looking for advice on the exact opposite and haven't had any luck.

The question in short:

How do I go about writing published adventures for other people to pick up and run? What info is necessary, what info is unnecessary, and what is just distracting?

Tangential background:

In my decade of GMing I have used a published adventure exactly once - it was an awful experience, nothing went to plan, and I felt much more prepared than I actually was. I have never done it since.

However, I am currently writing my own ttrpg system. It's going along great but before I even think about promoting an alpha release, I want to create a "Pick up and play" set - including basic, pre-created character archetypes and an adventure/mission, so you could jump in and try it out whenever.

I usually throw my players into a sandbox and plan every session individually to avoid burnout and to play my own little strategy game, if you will. That type of preparation just does not work when I'm trying to give someone else a prerendered package.

So I'm turning to the hive mind:

• What's the info you would be looking for when running published adventures(, module campaigns, what have you)?
• Which parts are often given but you almost always ignore anyways?
• Which parts are just distracting and make you feel like nothing is going to plan, or even cause your players to often go "off rails"?

I'm not looking to write a whole campaign - I'm aiming for a mission of around two sessions, just in case that's important to someone's advice.

As always, any nudge is appreciated. Thank you in advance.