Yes I do tell the teachers I appreciate them. In the 70s and 80s many schools subscribed to the theory that your spelling would be ok if you read lots of books and that you didn't need to be taught it specifically.
I was reading 8 books a week (as many as I could get out of the library) when I was in primary school, but my spelling was always quite random. I only began to care about getting it right and learning the rules at university because I was having to fill in job applications and so on.
I think it's fabulous that my dc are being taught to read using phonics because learning the whole word way, as I did, doesn't help you work out unfamiliar words. I didn't learn the word homophone until I was in my twenties and so I think it's great my year 4 child has homework about them!
I'm still not sure about how to talk about verbs, clauses and so on and I think learning Latin would have greatly enhanced my reading. I'm jealous of my dh's grammar school education that drilled him in the above.
A secondary school teacher could quite easily have had the same schooling as me and taken a first degree where spell check got them through. The PGCE is a year long course which has most of the time in the classroom teaching you how to teach and not how to spell.
As for having no respect for teachers....I'm assuming you home educate then? Leaving my kids with people I didn't respect would be very hard. Respecting doesn't mean I won't question, but it does mean I'm in awe of the task they face every day.