I find that the toughest part about adding features isn't figuring out how it fits with the existing design and adding complexity—it's figuring out if you should build it in the first place.

Feature requests are about supply—the thing you're selling—not problems. When the CEO or users or whoever offer suggestions, it's not about a problem they have. It's about a solution they want. It's a cognitive trap to conflate the solution with the problem and you can end up building something that no actually needed in the first place (re: the Product Death Cycle).