To me, the most "useless" district has to be the entertainment complex. I've basically never run out of amenities until I start putting up neighbourhoods in cities, so I don't think I've ever built an EC until that point. Which defeats the purpose of them being available starting in the classic era.
I think they're also hurt by the fact that since they provide "local" luxuries, often all that really does is just give you more amenities that can be spread to other cities. So building an entertainment complex in one city is probably more likely going to help out a completely different city in the empire.
Now, I'm not sure what's best done with this. I almost feel that the best way to handle it would be to combine the theatre square district with the entertainment complex (probably still keep the same EC name, give it a base of +1 amenity plus the regular theatre square bonuses), and simply give you a fully free choice of buildings. Basically, you can build any 3 of the 6 or 7 buildings possible, in any order. So you would essentially be able to get culture and/or amenities from the district, and you either have the choice to build the cheaper earlier buildings to get a smaller bonus, or you can hold out for the more expensive later buildings to get a bigger benefit. To me, that would almost make this a must-build district in most of my cities, as you can then customize it to the needs of your empire.
I think they're also hurt by the fact that since they provide "local" luxuries, often all that really does is just give you more amenities that can be spread to other cities. So building an entertainment complex in one city is probably more likely going to help out a completely different city in the empire.
Now, I'm not sure what's best done with this. I almost feel that the best way to handle it would be to combine the theatre square district with the entertainment complex (probably still keep the same EC name, give it a base of +1 amenity plus the regular theatre square bonuses), and simply give you a fully free choice of buildings. Basically, you can build any 3 of the 6 or 7 buildings possible, in any order. So you would essentially be able to get culture and/or amenities from the district, and you either have the choice to build the cheaper earlier buildings to get a smaller bonus, or you can hold out for the more expensive later buildings to get a bigger benefit. To me, that would almost make this a must-build district in most of my cities, as you can then customize it to the needs of your empire.