One of the most important skills a product founder needs to have is evaluating the quality of a design.
If the design is good, we can ship products. If it's not, it's back to the drawing board. If we ship bad design we lose customers, but if we err on the side of waiting forever we'll never ship at all.
So how can we know if a design is good or not? Of course design is somewhat subjective, but there's a surprising amount of literature that can help even non-designers get reliable insight into design quality.