Manually manage library

Okay so I don't use iTunes very often because I absolutely hate what they've done with the interface. How it's glazed over and overly simplistic (v6 was nice and user-friendly). But recently while on a trip I noticed that when I setup my iPhone 6 (on the same computer with the same library as now) a lot of my albums are not sorted properly and missing artwork. It was all present before but somehow it was lost in the upgrade. Now call me old fashioned but I hate the whole sync thing. I really think it is a stupid way of doing things. I've always preferred to manually manage my music and have done so ever since my iPod click-wheel. However, when I plugged my phone into my computer today which is likely the first time since I setup my iPhone 6 (see above interface issues). I'm now locked out of my library unless I sync. Why did this happen and how do I undo it. I do not plan to sync anything. I do not backup my iPhone. I have pictures and settings I do not want to risk loosing just because iTunes wants to be more important to me than I want it to be. It is just a tool to manage my iPhone. Not in any way my media centre.

All of my music is on my computer but it is not all mirrored on my phone. Nor do I feel like going in and sorting what goes and what stays. I already have that on my phone when I set it up before. I should not have to deal with this again yet in apples infinite wisdom, resetting ownership of a device and/or library is a fun way to entertain the support department.

Any help would be greatly appreciated while my growing hatred of this software in it's generations grows.