Too many people want "clean" and "modern" designs because they like the way it looks, usability be damned.
Folks look at the cool designs from that era (and late '90s Windows) and want them back. You can't have that and $0.99 apps. If you try to get that kind of design with today's design budgets, you get exactly the kind of Y2K photo app skeumorphic design that everyone hated.