The itunes interface hasn't changed much in the last 13 years. Not many software products go that long without a major reskin, especially seeing as it came from a company that prides itself on it's progressive design.
I quite miss the brushed metal look. It is interesting that you could take OSX from back then and put it in front of someone today and it'll behave mostly the same. Sadly the same could not be sad about mainstream Linux environments (GNOME3, Unity etc.) or Windows 8/10. Windows 10 you can to some extent. Thought provoking.
Then Panther (10.3) came along, and Finder went "Look at me, I'm your filing cabinet!" Eeeeeh, ok I guess? That's when it started to feel tacky and overused for me. Maybe because I only ever had one iTunes window, but the message of "You have 4 filing cabinets open on your desk" is a little bit weird.
As far as iTunes in general goes, I wish it'd go back to being a simpler MP3 player. They've got so much stuff in it (iOS device sync, music store, internet radio, Apple Music, podcasts, iTunes U, whatever else I've forgotten).
All the different layouts, the way the playlist sidebar appears and disappears, the multiple navigation schemes sharing one bar (pick source on the left, sometimes an icon and sometimes hidden in a dropdown, change view layout in the center) doesn't work well. Just the other day I switched modes and then was thinking "Wait, where did the list of recently added items go?" I found it in the albums layout by clicking through random stuff until I got the one I wanted, but I feel like if an MP3 player makes me hunt for something then the interface has failed me. The iTunes version screenshotted here never had hunting.
Family members have asked me "Where did X go?" on more than one occasion after the redesign, and I can't answer is quickly as I'd like anymore...