A survivalist is forced to defend his post-apocalypse community from anti-technology fanatics and a traitor within the community's leadership.

I agree with the guys. Goal is missing. A survivalist i understand means, that the guy does not care about anyone just beside himself? Its a nice irony that now he must defend the city and actually he starts to care. But why? What makes him special? For that reason survivalist does not work. He don't have a motive to start care. And is forced? Like they put a gun on his head and told him to shoot on other guys? Maybe some woman is involved? Or family values?

The day that your story starts.. what is different? What is the inciting incident? Do the AT people attack for the first time? You need a reason for the story and then I agree with Timmyelliot, your MC needs a specific goal. Try not to use Forced.. always better with the MC chooses to go on the 'journey'. There is always a choice, even if the other choice is death, it's still a choice.
Good luck, sounds like an awesome idea.

So far it feels like a situation.

I'd like to also see a goal and the stakes.

In other words-- a survivalist, forced to defend his community from ......, goes after some goal.