I don't understand non-breedable part, mosquitoes are a part of a food chain as everything else, surely you don't think eliminating them will have no consequences?
Ae. aegypti is not native to California. We won't miss it.
This is addressed in their FAQ as well: "The general consensus among scientists is that the ecological impact of removing Aedes aegypti mosquitoes from urban environment would be small. They are not a significant food source for other animals and are invasive to many areas. The main ecological impact would be to restore the ecosystem to how it was before the mosquitoes invaded. Debug team is committed to working with communities and regulators to ensure the safety and acceptability of our field trials and releases."
it is unlikely that other mosquitos (that don’t carry disease) will fail to fill the niche
It would eliminate a natural control mechanism on humans that's for sure.