i've used them ever since Wirecutter first recommended them, i think going back to the iPhone 7. they're cheap and durable—never broken a phone while using them. but they will discolor on you, especially the clear ones. but even the blue one, which is my daily driver, has discolored. (silk replaced them each time)
but i recently got my first caudabe. it's about twice as much as silk ($24 vs $12), but the quality seems to be twice as good too. just a tighter fit and finish, especially on my XS.
there's nothing wrong with silk cases per se, but if you spend a little more, you'll get better quality too.