This thread is not monitored by any software engineer at Apple.
They won't read any of these complaints nor will they make any changes to their software. Other than venting your frustration, posting here won't make them "fix' itunes 12.1 or 13 or 14. Apple doesn't do that- they make a change and they stick with it without ever reverting back to anything, no matter who complains or how many threads and replies this topic gets.
You may find a way to roll back to iTunes 11 so you can see the GUI the way you want to, but its only a matter of time before iOS 8.1 or something comes out that REQUIRES you to be on iTunes 12 before you can ever run the upgrade. Then you'll have no choice - accept the iTunes 12 interface, or keep your device without features.
This thread mine as well be closed because it's just people saying "Me Too!" and it will never, ever make any difference to any release of itunes in the future. Apple doesn't work that way. What YOU want is not part of what they develop. Again I'm not trying to be mean to Apple. Years of seeing how they operate tells me without a shadow of a doubt they whatever you complain about, they won't change because they have a singular focus and they obtain that focus regardless of who complains or how loudly. The only exception I can think about was the bumpergate of the iPhone 4 and corporate even told them flat out not to give in and offer bumpers regardless of the millions of people reporting the problem. If you think you can make a forum post about iTunes 12 and some GUI side panel issue that'll change the way they program their software, you're sadly mistaken. I hate it too but it's the way Apple is.
I'm sorry but you're stuck with it. There's no way around it.
They may fix bugs in the GUI behavior but in the end you're still using the same interface. If you don't like it, don't post here and complain.
If you are really dedicated to trying to get Apple to change their policy about not involving the community when they make changes to any of their products, the only way you can make a difference is to NOT buy Apple products in the future. Speak with your wallet. It's the only way Apple will change.