Sewers I mostly build for the inspiration. I think over time, they have added a lot more sources of housing, so that always reduces the sewer's benefits. I do think sewers should have a bigger effect the bigger a city is, so make them +1 housing per district in a city as a start. In a perfect world, they would essentially be the modern upgrade to aqueducts. Like, it's kind of dumb to be building tanks and stuff, yet you still sometimes build an old fashioned aqueduct to ship water around and help your factories out? Ideally, it would be great if you could somehow merge it all together, so that somehow when you unlock sewers, you can dismantle an aqueduct and place another district in its spot. I think if they also removed other sources of housing in the mid to late game, that would help too. Like, if New Deal was simply +2 amenities in each city without the housing bonus, then at least you're a little squeezed more for housing, enough that being able to build a sewer to give 4 or 5 housing makes sense.
Food Markets I do actually use them a couple times, but most of the time, since you can only choose it or the shopping mall, I agree it's underwhelming. They have boosted the shopping mall to give multiple amenities and tourism, as someone suggested above, if the food market added some secondary pieces, that would help too. I also would like it if you build 2 neighbourhoods in the city that it would let you build both of the buildings. Would at least open up some new avenues for growing larger.
A lot of the other mid to late game ones are still fairly weak. I seem to always find myself being able to like 2-turn late science techs without even needing to build more than 1 or 2 research labs most games. I kind of feel at the very least, cards like the International Space Agency should be something like +5% science per CS suzerain in each city with a research lab. (And similar for broadcast tower and the culture card). Would seriously nerf those cards, but would at least force you to build research labs for the bonus. Arguably another option would be to make research labs and broadcast towers more like a regional building - although without overlapping area effects, you still wouldn't need more than a couple of them to cover your empire.
Others have mentioned, but yeah, all the aerodrome buildings are also seriously weak too. Would love to see a larger tourism emphasis to them, and even could combine their bonus with like the national park or ski hill bonus too. So maybe each airport building should give like +25% tourism to all tile improvements in range that give tourism? I mean, in theory you should be able to gain a lot more tourism from Moai or stuff too if you can fly there.
