I’ve heard this a lot, and as someone who is just about to jump back into iOS after a 7 year break, I’m inclined to just defer to this opinion. But I’m curious

I’ve heard this a lot, and as someone who is just about to jump back into iOS after a 7 year break, I’m inclined to just defer to this opinion. But I’m curious what this means, specifically. What would a good example of a serious UI, in your view? Not looking to argue - I’m genuinely curious.