I think the main reason for lack of Domination Victory is most likely because the AI just go full genocide even after taking enemy's capital, thus racking up a lot more warmonger penalty than needed, thus to have a Domination Victory likely they would have to complete painted like >80% of the world to win (thus estimatedly perform 4 times better than the rest of the world combined in score), while other victory only requires you to be about x1.5 times or less score than the next runner up.
A better fix would be changing how Domination Victory is decided, like controlling more than half or 1/3 the world's cities/population after year XXXX instead. That way AI would have an easier time to win through warfare, and for player who want to stop a Domination Victory they would have to be a lot more active in weakening the top contestant, instead of just ignore them to focus on defense and stall for time for other passive victory type like culture or science.