Well, I don’t know if it’s just me, but I find unique improvements quite underwhelming, especially compared to unique buildings that offer much better bonuses.
I recently played as the Mississippians, and while they are a great civ for an economic victory, their unique infrastructure feels pretty negligible. The same goes for the Mughals and their Stepwell.
Independent People improvements haven’t been very appealing either.
I feel like tiles now have much more value than in any previous version of Civ, so improvements really need to be worth the “cost” of using up a tile.