You explained this very well, in my opinion.
I believe that the majority of teachers are very good. Few go into the profession if they don't have the best interest of the children at heart. Often it's not so much the teacher themselves, but the system rules they have to work within which can cause them to fail to cater for some of the children. The only teachers I've encountered who still excel for every pupil have been ones who work tirelessly, putting in endless hours at home in order to reach every pupil's need. I've had teachers admit to me that their hands are tied with regards to what they can provide for my eldest, who was way ahead of their scope at times.
Sadly, I've also encountered the odd teacher who just didn't really care about the children or showed favouritism. One of these types of teacher was the turning point for me taking them out of the school system.