Or What Can a Teacher Teach Me?
In the 20 years I've spent learning the guitar, I've had five teachers, all of whom taught me different things.
When I first started taking guitar lessons in the early 90's, I read guitar magazines and books (we hadn't even heard of the internet then!). I didn't really know if I was doing it properly, but at least I was playing the same notes that Slash was playing on Appetite for Destruction, so I was happy. After a few years of this I got a bit stuck, I wasn't progressing and was quite frankly getting bored. I tried to learn a bit of theory, but wasn't really able to apply it in a meaningful way.
My parents, who probably were a bit sick of hearing the same songs, booked me in for my first lesson. In that lesson, I learnt that I couldn't play in time, that my posture was causing me pain, and why the notes I was playing didn't sound the same as when Slash played them. He passed on this information with kindness, understanding and patience. It made guitar-playing feel all shiny and new again and he could answer all the questions I had.
Now, what if I had seen a guitar teacher from the very beginning? I would have been light years ahead of where I was and I would have been able to do all the impressive stuff months earlier.
I was scared to see the teacher the first time. Would I embarrass myself? Would he tell me that I had wasted my time? He did none of those things, because he was a good teacher and had gone through the same struggles that I had in learning the instrument.
These days, I love youtube videos and web articles and they help my playing a lot, but they can't act as a sounding board, keep me motivated nor tell me what scales I should work on to play a solo like the one I just saw online.
So to wrap this up, its true that not all guitar teachers are good, and you need to find out for yourself. I would recommend going to a few teachers until you find one who you feel comfortable with and who can help you achieve what you want. Maybe I am not the right teacher for you, but somewhere out there is a teacher who can help you be the guitarist you want to be a lot, lot faster.