I prepared a West Marches style game for my game group and invited some other folks along. It didn't go well.

I'll admit I'm a bit sore over it. I think it's fair to feel disappointed. I'm trying not to allow myself to feel bitter. You have the right to run whatever game you want, but nobody has a responsibility to join you. The game had issues that made it unpalatable for some players.
The campaign pitch was this: You're new arrivals to The Snarl, a jungle hemmed in on all sides by mountains and coastlines. Its history promises many buried treasures and lost settlements. A war and cataclysm elsewhere on the continent displaced huge swaths of people a decade ago, and those without better prospects (or who are on the run from the current administration) might make their way here to seek their fortune. It has a reputation as a hideout for pirates, robbers, and witches. Stake your claim in the jungle and make a name for yourself!

My own system

I shopped around for a long time looking for a system to suit my needs. I knew I wanted something rules-light. My setting needed to support magic, but I didn't want it as a character option: The Snarl does contain magic the players might eventually access, but there aren't wizard's towers in every major city like in D&D. Encumbrance needed to be a concern, but I didn't want the accounting to become burdensome.
The Black Hack, 17th Century Minimalist, Tiny Pirates, and DURF all had elements I liked, but ultimately none of them were quite right. However, the nice thing about a lot of the OSR systems is their compatibility. I was able to take 17th Century Minimalist as a base and graft on the subsystems I liked most from other games. I stripped out the classes from 17th Century Minimalist and instead used a Traits list cribbed mostly from Tiny Pirates. I took the Stress system from DURF and grafted it onto a simple slot-based inventory system. I tweaked the armour rules to more suit my taste.
In the end I wound up with something that I liked.

Expectation

Matt Colville introduced me (along with half a million other people) to the West Marches format back in 2017. I loved the concept: I get to do all of the fun world-building stuff while my players handle the boring scheduling stuff! Playing with a bunch of adults with busy lives and infrequently overlapping availability, this seemed like a good fit. I'd already been running an episodic campaign to help address that same issue, but over time it had morphed and become something closer to a traditional campaign. A West Marches game looked like it would accomplish what my previous experiment did not.
I seeded the setting with several different factions each with their own struggles and ambitions. I divided it up into several geographic zones with interesting creatures and encounters. Ruins from the region's history, still brimming with treasure were strategically placed for the players to find.
My hope was that as players delved into the region and discovered things, each encounter and location would hint at more things left undiscovered. It was my hope that the players would seek out ways to achieve their own goals in the Snarl, and the cool stuff I peppered in would give them opportunities to do so.

Reality

Some things went well. They discovered old ruins that had become the nesting site of enormous terror birds. They met a witch on the lam from the cult who trained her (and then encountered her hunters and engaged in a tense battle which established a great recurring enemy). A trio of fish-folk tried to drag them down as they crossed a river, which led to an expedition to find where they live and steal their treasures. The players inadvertently burned down a monkey hideout and were harassed by monkeys hell-bent on revenge. Some memorable moments came out of the game and I think there were nuggets of real fun and intrigue in the campaign's short run.
Some things didn't go well, though. It became clear after two sessions that the wilderness exploration rules I'd bodged together needed to be streamlined. Too many dice rolls were resulting in "nothing happens, roll again." I made adjustments to my procedures to ensure that I would not ask for a roll from my players unless it would have an effect on the outcome. Obvious enough when written out, but it meant more careful attention on my part as a GM.
Players complained that there were no opportunities for the characters to interact with one another outside of combat. This was absolutely fair. I had spent so much time agonizing over how to run a West Marches game mechanically that I entirely forgot to consider how to run one narratively. We spent a long time talking after what turned out to be our last game discussing how to fix this and I think I am in a much better position to address this now.
We also had trouble with a mismatch of expectations. I was clear from the outset that the priorities in a West Marches format would be a shift from our standard, storytelling games: You're responsible for tracking your inventory. You start and end in town. The dice fall where they may and we deal with the consequences. I am always committed to being a fair GM and will err on the side of player enjoyment when some rule is unclear or we mess something up, but this format is also somewhat less forgiving than what they might be used to. Unfortunately this wasn't appealing to some of my longstanding gaming group. This, more so than the other issues, was difficult to solve without abandoning the premise of the West Marches format (a point on which I'm unwilling to compromise).

Death

We played a total of four expeditions (one of which was split over a few sessions, contrary to the intended form):

1. The players struck north and discovered an old aqueduct, some kind of ancient building, and struck a deal with a renowned circus ringleader and pulp adventure novelist to recover some eggs from the giant terror bird which lived within.
2. The players went west and discovered a strange ring structure of unknown origin. They met some folks on the hunt for a young "thief." Later they met the thief - Tulsi - camped out in a ruined town, and fought off her pursuers (including a big weird homunculus).
3. The players escorted Tulsi far south to Mosquito Bay at her request. They were attacked by fishmen, burned down an old watchtower (pissing off some monkeys), got lost, and were saved from near-death from a bug man who fled into the jungle. They finally got to Mosquito Bay where they found work for Tulsi, ticked off the local ruffians, and learned they didn't much care for the predatory mercantile outfit that set up shop recently in town.
4. The players followed the river north to look for the fishmen settlement. They discovered a small outpost and looted it, and then engaged in a long run through the jungle in an effort to escape. They wound up fighting the fish men on the same bridge as in the previous session, narrowly keeping both their lives and their loot.

Each session highlighted some shortcoming of the system. I enthusiastically retooled the system each time, but I think the stumbles were enough to kill my players' enthusiasm for the game. One player (who happens to be my dear brother) pitched the idea for further expeditions, but three such attempts went by without so much as a peep from any other players. I took that as a sign that the campaign was dead. Nobody has chimed in since.

What will I run next?

This game highlighted some of my GMing tendencies: I love world-building, but tend to over-plan. I am great at designing dynamic action sequences, but struggle with character work. I get very invested in whatever I'm running without confirming that anyone else is invested in the same thing.
I'd like to spend some time this year explicitly pushing against those shortcomings. I'm thinking of running a few short form mini-campaigns (to the tune of 6 sessions) with little more than a strong hook, a robust session zero, and a willingness to be flexible and follow my players' lead.
The things I enjoy in TTRPGs aren't BAD. I think the skills I've developed will serve me well no matter what I choose to do. I don't intend to give up on running the types of games I like best. But everyone has weaknesses, and I'd like to work on those muscles I've developed the least.

It lurks just below the surface, ready to rise when the time is right

The game will always be there ready for the right group. The rules I wrote, the map I drew, the factions I developed: barring both a solar flare and a house fire I will always have some version of those things available. I am putting them away for now but I'll hold out hope that some day the right folks will come my way and strike out into the Snarl once more.

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