AkaTsuki-chan
Short Answer: Yes.
Long Answer: Yes. 1 on 1 voice lessons are incredibly useful, and you will benefit from them an infinitely greater amount than if you just studied on your own. Qualified vocal instructors can pick up on and fix errors in your technique which could be detrimental to your overall sound and to your vocal health. It is very hard to be impartial and pick up on these things yourself. I've been without lessons for a little over a year now and the amount that my voice has deteriorated is astonishing. By most accounts, I still have a nice enough voice, but my control over my high register is significantly weaker and my stamina is nowhere near what it once was.
'Cookie cutter' voices don't really exist. Certain qualities are universal to healthy singing, so if you don't want your voice to be healthy, then by all means - keep doing what you're doing alone. A good teacher will work with YOUR voice to make it sound the best it can sound.
I'd need to hear your voice to really hear what you're talking about with 'unique qualities.' If you mean you sound like Macy Gray or Louis Armstrong, then yeah - any voice teacher worth their salt is going to try to change that because that s**t just ain't healthy.
I just feel like I see a lot of singers who've never had a real voice instructor their entire life who sound fantastic, and I've heard a lot of people who have that just sound...well.... Uninspiring.
By 'cookie cutter' I mean the voices that you couldn't pick out of a crowd. The ones who can sing, but aren't standouts. Someone that's healthy, and knows how to control a decent voice isn't always exciting to hear, so I guess a lot of it must depend on the teacher.
I have a little rasp to my voice, but I wouldn't want to erase that. Usually the only thing I tend to do that causes me to stop is trying to sing low notes. That's my weakest spot. I don't understand how people like Christina Aguilera can sing without loosing their voice after one song haha.