What company’s UIs are at the forefront of design, and why?
I'd look at if the UI/UX is getting the users from A to B in as few steps as possible, and as simply as possible. If it feels too complicated, then your designer needs to iterate. Looking at trendy screenshots is not something I recommend. Looking at design patterns might be, if you notice a UI problem and want to know best practices for how it may have been previously solved:
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