Most southern Yemenis don't want unification. North and South Yemen were separate countries for decades. When unification first happened there was optimism but South Yemen (which is about 20% of the total population of Yemen) was always hesitant about how little political power they'd have. North Yemen is 80% of the population and, today, almost entirely controlled by the Houthis.
I don't think native Yemeni are motivated enough to fight for unification. That's why all the fighters are mercenaries hired by the UAE or Yemen
We've seen Sunni majorities in Syria and Lebanon run for generations by oppressive Shia-supremacist regimes, so while I agree that the resistance against Ansar Allah doesn't have a lot of local legitimacy, I think you have to be a little careful about reading legitimacy into the dominant power in Yemen; once a group gets the upper hand, it can be hard to shake them off. There's a whole interesting history to how Yemen got here.
I don't think native Yemeni are motivated enough to fight for unification. That's why all the fighters are mercenaries hired by the UAE or Yemen