All the big companies now are moving towards minimalism. Google, Apple, Microsoft, you name it. Especially when it comes to UI, the best designers are more likely to make use of simple and clean icons and interfaces. It just makes sense, you need something descriptive, unambiguous, yet still looks neat.
So for your next UX/UI project, you might just want to use these square line UI icons from Graphic Pear. Consistency is key in any interface; the size, proportions, and aesthetics of the icons all contribute to making an interface look uniform and easy to get familiar with. Avoid creating a messy UI using these line icons. This vector set of 42 square icons comes in a single AI file.