Earlier quoted context omitted.
Teachers should be judged based on student evaluations - but those evaluations should be deferred until, oh, 10 years later when students can honestly and dispassionately answer the question: "did that teacher enrich my life, prepare me for the livelihood I'm actually earning today?" Of course, administrations can't wait 10 years for feedback, more's the pity.
Not to mention I'm not going to remember any of my professors in 10 years.
Not all of them, no. Of course not.
But you remember the great ones, and you remember the god damned awful ones. The great leave an emotional mark on you, they inspired you to go into their field, they showed you something that wowed you and has stuck with you over those 10 years. And the damned awful ones leave emotional scars that don't fade, and you'll talk to old veterans/classmates about them like you did a tour of 'Nam together...