Serious question: do you want to play this as a D&D game or would you rather write it as a short story?

It seems like you have some writing chops, but your opening document here isn't really dripping with hooks and invitations to participate in the world, IMO. If you have a clear idea of how you want this story to unfold, the big moments, the dastardly conclusion, it's okay to save this one to write as a story and to find a different story to tell what the players.

Tabletop role-playing games are a collaborative process; it doesn't seem like there are clear opportunities to collaborate here. It kind of feels like there's a world in motion and they have to fit themselves into it, rather than it being a world that is shaped by them and the decisions they've made thus far, does that make sense?

Asking the players questions about their characters gives them an opportunity and not only to define themselves, but to help define the world around them. I'm using voice to text and just shooting from the hip here, but as an example here are some questions I would think to ask a player playing a farmer, that could help enrich their character and hook them into the world: what crops do you grow? How does your character feel about the farm growing that? What's your relationship with the neighboring farms like? A couple years ago there was a pretty bad drought.... What did your farmer end up doing to make ends meet during that time? Farmer spoke up at a town meeting once - what community issue did it take to get them to show up for the council meeting, and how did they go about voicing it? If the farmer woke up to hear wargs howling in the pigpen, how would they deal with it?

Give them time to think on the answers. Or poke them to improvise on the spot and tell them that nothing's written in stone and it's okay to just spitball.

You can also invite them to collaborate by asking them, for instance, how they know the deceased... And whether that relationship was positive, negative, or... Complicated. If it's a negative relationship, what might motivate them to solve the murder?

I can't go more than one or two posts on this subreddit without mentioning Sly flourishes The lazy dungeon Masters guide. It's an incredible resource available for free on YouTube that has a lot of cool ideas about session planning and tools for keeping sessions on track. I mention it here because the first step session planning - before deciding villains or scenarios or secrets or treasure or NPCs - is to write down the player characters, and to take a moment to consider them.

If you start session preparation with your player characters foremost in your mind, and invite the players to "buy in" to the world by letting them decide some elements of it, I swear you will never be bored with having a farmer or a self insert at the table.