Just wondering why Ajins won’t start a rebellion. They are generally stronger than human...

I also asked myself this question. And to be honest the logic in this world of Arcana is very melodramatic and unintelligent.
It's a frustrating soap opera. Many problems would have been solved, if the characters were more self-confident, honest with each other and communicate better.
To be honest, I feel like the ending of Reimei no Arcana was very rushed and abrupt.
I ve read other works of this author and she has the tendencies to make many of characters going through endless abuse, sufferings and tears until an unexpected deus ex machina appears.
Edna/Eden from Light & Shadow was able to change the status quo through her courageous and wisdom. She was able to free herself alone from abuse, allied herself with good men and manage to improve and save lifes despite huge obstacles and threats.

They are a small minority and overpowered by the number of humans.
To make sure, they are not able to revolt, every couple is only allowed one child (or twins, if they get lucky), so their population drops from generation to generation.
Also every man has to enter the army, until they are to old to be a tread and women have to work as prostitutes until they are worn of, afterwards they have to do hard manual work.

That's very shocking, depressing and tragic.
Kinda remind me of all indigenous people in the real world.
But what I learned is that they won't go extinct so easily and they still keep fighting despite all the transgenerational traumas.
It is not unrealistic to claim that a smaller country/population can win against a bigger one. Take for example: The Vietnam War. The North Vietnamese army was able to win against the US army even though they were badly damaged by AGENT ORANGE.

I think the author explained it in the beginning. It's like chaining baby elephants. No matter how huge they grow up to be, they have psychologically been broken into that they never think of rebelling.

Coupled with that, they probably don't have a good leader to lead the rebellion.