Why is there so much hate towards Duolingo in this community?

This is the second Chambers community for language learners I’ve been a part of (the other one was r/LanguageLearning) and both chambers are filled to the brim with anti-duolingo sentiment. I’ve been confused about it for a while but figured I’d ask here because I like this subreddit. I agree that the algorithm is kinda whack, and it’s not perfect, but why does everybody seem to hate it so much?