Man I could see having 8 cities up and running by turn 87 but having multiple districts in more than one or two is just, literally how lol. But anyway as people have been saying the issue isn't with production being too slow, in isolation, I mean, I and I'm sure many others feel that way. But the problem is in relation to tech and civic scaling. They are just not even close to being balanced, at all, with a decent amount of development you will blaze through the tech tree from medieval to atomic in a few dozen turns. It's pretty ridiculous. Like, okay, building districts takes a while but like, my city started building a commercial hub in medieval times and now it's the industrial age and we have factories and steam power and they're still working on it? Units aren't as bad, unlike districts I don't inherently feel their cost is too much and upgrading is always worth it, but they are still out of sync with the tech tree, if you start building mid-late game military in your low priority low production cities that aren't using trade routes, they'll be obsolete by the time they get built.