Stuff I considered putting on the review comments, but didn't want to clutter them. I hope this context helps to understand what's going on with this adventure and how to get it back to it's vision:
I was going for a mad max kind of vibe, there's a lot going on in this sandbox and while the players only have the directive to go from left to right there's tons of things to catch at their cloaks and stumble over on their way over. I wanted each little area to be interesting enough on its own players would give up on or detour from the main quest to participate in it. I think giving players fleshed out NPC's to get their interest (like with the rival parties) works best for 5th edition players used to storygaming.
It's loosly tied together with an anticolonialist framework, made to make players examine their role in DND's kind of standard "move into a place, clear it of monsters that live there, set up camp" kind of playstyle. Like land appropriation, it frequently tempts players with deals that are too good to be true, but confronts them with the consequences later.
As for the mist theming, It's fairly binary. For most of the map there's a 1 in 6 chance it's either on or off, and it's always super thick for the rest of the map. Not a lot of room for descriptive elegance in the keys when it's a blanket of fog or nothing. I figured players would have plenty of experience interacting with it mechanically as a navigational hazard that drenching them with description wasn't necessary.
This was originally some kind of 3 part series with stuff downriver, but I introduced the gold rush stuff and cut all that to just get it out quickly. I think the gold rush is at the very least less confusing.