I assume it's because of Liquid Glass. It's absolutely undercooked as a design system, but Apple knows which way its bread is buttered. So Liquid Glass on iOS is where it's the least bad, and I switched there knowing that. It was exactly as I thought: a regression in most places, but still manageable because Apple is laser-focused on the iPhone.

I didn't upgrade my Mac and at this point I'm wondering if I'll ever be tempted to update until I see what they do with macOS 27.