I wish we had more Design Themes. Personally, I'm pretty much happy with the voting process. It's us, the players, who decide the winner. I've heard some say that they just vote to get the free item at the end or some have even said they only vote for the players on the left or right. If they don't care whether a Night City challenge submission is in the daytime, then what can you do. I like the flexibility the game gives us to do what we want and make & learn from our mistakes. You also have to remember that some challenges are interpreted differently such as the Great Wilds challenge. Some have interpreted it as a Wild West type challenge while I think of Las Vegas - a city built in the desert. Because of that, I think it's hard to put too many restrictions on the players. You also have to consider that some people don't have water and trees to build with. I saw a player complaining a few days ago about needing to have a certain amount of resources in order to do well in the challenge. And then you have some people who just don't understand how to actually make a city. I've seen people that don't understand why residentials who live next to a polluting industrial building aren't happy. With some trial and error, their skills and knowledge will improve.
A common complaint I hear is someone complaining about a design that looks worst than theirs or, for instance, a person that doesn't have a river for a River Town challenge has like a 4.0 rating. We have leagues and those in the lower leagues don't have the competition that the higher leagues have. I was scoring 5.0 on stuff in the lower leagues that probably would've gotten a 2.0 in the Platinum League. I think it's good to have an area where the newbies can kind of test the waters and the level of difficulty isn't high. I think the way the game has it set up where we're compared to other people based on our ELO is a pretty good idea.
There are some people who I've seen complain about not getting a high score for their city but if you look at their city, there's a good reason they didn't get a high score. They might've took a while putting the city together but it's just not on the same level as the people their competing against.
As for the Disneyland cities, I agree that some of them are not on theme and they can become repetitive but it lets you know that people like a WOW factor. That's why those "cities" are winning. I usually try to include unique shapes in my designs in an effort to distinguish myself from other players. There are certain elements you can include in your own city that will get you votes even if you didn't finish the city (My own experience) and still score a 4.0 in the Platinum League. The more you play, the more you learn. At this point, I'm just having fun designing the cities I want to design. If it doesn't do well, oh well. If it does, then great. If you're interested, there's actually a Facebook group for Designers. They are some of the people who've won the whole thing. Maybe sharing and talking to other designers will help you improve your own designs. https://www.facebook.com/groups/1106669973602079