The job assinment UI could use some improvrments, such as:
1) Job priority! Set which jobs you want a planet to focus on, or at least what resources. This is something that exists for sectors, so it should be possible for jobs.
It would be extra awesome if we could set ratios.
2) Amenity AI. Set a threshold of the minimum amenities before a pop is moved over to amenity production. Amenities don't do much except act as a second resource tax, at least for MS's, so there's not much benefit to maximizing them - the stability bonus for high amenities is too small.
3) Allow for click-dragging pops between jobs, instead of having to close off multiple job types until they move. That alone would make it much less annoying.
Habitats do seem weak for the cost. Their small size and lack of really unique buildings means that they're basically a planet full of building slots and little else, which makes them great for alloys, consumer goods, and refining, but little else.
If they want Habitats to be energy/research platforms, then they should have fewer building slots - like 5 to 10 total - and truly unique buildings that provide large boosts to energy production or research. As it is, there's just the Energy Nexus and Super Computer, so even if you use building slots structures to house all your pops, there are still tons of empty building slots.