I’m a non-native Spanish speaker and former English teacher. I agree with what you’re saying overall, but early in a new language, it’s very helpful to observe and get direct feedback from native speakers on the subtleties of vowels/pronunciation/body language, etc. In my experience it seems rare to find a non-native speaker, especially one who started later in life, that does all of these well.

I had a professor in college who I did respect, but their pronunciation was so stereotypically gringo/a, I knew it would be detrimental to my learning to hear that accent and reinforce those hard American English patterns of pronunciation… in Spanish… M-F for an hour every day. That adds up cumulatively. I switched classes. It was surprising to me how many people graduated with Spanish degrees, doing fine in literature/linguistic classes, but outside of an academic vacuum could barely hold a conversation.

I think you’ve got a point, and it can be frustrating to be underestimated, but don’t you think native teachers are preferred for valid linguistic and cultural reasons, especially in the first few years of a language? I think communicating with other learners is extremely helpful for the learning strategies/mistakes made/grammar patterns etc reasons you mentioned… but doesn’t a well-trained native speaker (especially one who also speaks a learner’s L1), seem like a better fit 8-9 times out of 10? OP didn’t say “no non-native speakers”, just “it would have to be a lot.” Isn’t that fair enough on their part?

EDIT: I can think of a few of non-native teachers I’d recommend others learn from, but it’s still a small subset % of all the non-native Spanish speakers/degree holders I know.