Zomboid is a great game, and the devs have been steadily working on it. They're not a very big team, and they live daily lives just like you and I. The process of creating a game like Zomboid is extremely complicated, time consuming, and tedious. Especially considering all the detail and mechanics that function behind the scenes of gameplay. Comparing Zomboid to other games like Left 4 Dead and DayZ is apples and oranges. Zomboid is a game that is striving to take everything into account to make the gameplay experience as realistic as possible, and it isn't a large game studio creating this for us. It's a group of guys/gals that decided to make a game one day. The thing that I appreciate about Zomboid is every time I look away, there is always something new being done with it. Granted it isn't a game changing update like build 41 every time I come back to it, but they are always smoothing out the edges for us and making the game more and more enjoyable. The thing I'm not understanding is why you are utterly shitting on the devs laps for listening to their consumers. Of course people want NPCs, you said it yourself. The world in single player feels somewhat empty and lackluster at times because cracking zed skulls and rushing for that last can of tuna gets old because you have nothing to compete with. Anyway, you just need to be patient, man. The devs really are just normal people like you and I. They can't just take multiple days off of work to get little done. There's a reason why the game has been in development for so long. I gotta say on that note, for a game that is still being built on it's foundation, it is absolutely outstanding for what it is. If you want a game like DayZ or L4D, then go play those games. Zomboid is striving to become something different. It doesn't need a story mode because the purpose and goal of this game is to survive as your average joe. Nobody really sees story mode as a fundamental piece of this game. You're the first person i have seen pitch that. However if you wanted that, you could always reach out to the modding community and learn to create something for yourself and others.
Have a glorious 2020, bud.