flossy well said.
Good MFL teachers have a really hard time and I suspect many find easier ways to make a living.
I have no idea if my DF was a good teacher, but I know she was a brilliant linguist who picked up European languages, like nursery child catch colds.
DD1 said her French mistress tried really hard, but she had just the sort of disillusioned set you describe. She didn't have the classroom management skills to deal with them.
Me, I just can't do languages at all, I'm dyslexic (as is DD1, hence her low set). I can't see and hear the internal structure of English words, without effort. Foreign ones don't stand a chance.
I'd love to be able to help DD, but I can't. She isn't the sort of child you can help, she is very clever and very hard working if she sees a reward.
With German she has never got the faintest inkling that work is going to get her anywhere.
The immersive, no English, curriculum lost her completely she just didn't know what was going on.
Her teacher is just unable to grasp that she simply doesn't know enough of the basics to do what she's asked.
At my school she would have gone down a set and perhaps got work nearer her level, but her school groups subjects in a way that makes that simply impossible.
Of course I'll be polite to her German Teacher, but I'd still rather not bother.
Honestly not turning up wouldn't be rude. Our parents evenings never run to time and your often forced to miss some people because you are the other end of school with someone else.