It would be beneficial to a lot of people to increase the contrast of some buttons on the UI, such as the one shown in the image.
The inventory slots have a purple frame and gradient around them for example, so a similar change for some of the interaction elements, especially when they're against a blurry gray-white background (as most of the game is now) would increase the ease of navigation.
It would also help the UI be more in theme/coherent as some parts look obviously new while others are sort of forgotten, also making the blur of the background slightly darker or lighter (the opposite of whatever is done with the buttons) can also make each shop offer and the navigation stand out more, and aesthetically pleasing shops most definitely won't reduce sales!