Well generally speaking, most of the time a civ's power budget is going to be spent in other areas if they have a UB. Whereas a unique district tends to get the spotlight. Look at Korea: as crazy strong as they are, they have a ton of their power invested in their Seowon, with their Civ ability dedicated to boosting it. The civ would play almost the same if you stripped away the rest of its kit and left in those 2 things. Whereas another powerhouse civ like the Aztecs have extremely powerful abilities and a good UU, but their building is pretty bad. It's there for flavor, and as anyone who has had to face AI monty's eagle rush can admit, that's honestly okay. That said, only UDs scale their cost over the game, and you can't rush buy them normally. And a late game district can cost up to 540, which is on par with the most expensive tier 3 buildings like a stadium. Although some buildings cough tsikhe cough are definitely still way overpriced. Everyone hates on them because when they were released: -Their UU was quite literally the worst unit in the game. It was inferior to swordsman, a unit of the same class and an era earlier. -Most players with some experience don't struggle to get chain golden ages anyways -City States didn't used to have it so good (i think they start with walls now?) they'd get swallowed up by the AI like no one's business of high difficulty. So you couldn't really even use GotWK&F because all the city states were dead within 100 turns. -Renaissance Walls themselves were a meme, and they had unique walls that give a whole +3 faith. They didn't even have the extra wall HP they do now. So all their bonuses are either strictly good on paper but useless in game, or are actively bad. Since release they made the khevsur not suck after a billion community threads and some detailed math showing that without it's special ability a khevsur was actually worth about 0.7 swords. They also buffed city state survival, and they just made the changes to rams and towers that boost walls. And they made the Tsike grant +200 defense strength instead of +100; and of course, the creme de la creme, 5 cheaper. Tsikhe could be free and people would still probably class it as pretty weak.