My wife quit Duolingo the week before this announcement after years of watching Duolingo prioritize attention manipulation over learning. She had a nearly 6-year streak and was on the paid version at the time, but realized that it wasn't actually helping her learn any more: she'd at some point begun maintaining a streak just for the sake of maintaining a streak. The best documentation for Duolingo's decline is this a…
Duolingo is really only useful at the A1/A2 levels anyway. Once you reach B1, you're pretty much past the point where the vocab and grammar basics from Duolingo is useful and you need to move on to other activities (watching TV in your target language, having conversations with native speakers, reading books in your target language, etc).
It drives me nuts that Duolingo's Japanese course does not explain grammar nor does it introduce new grammars fast enough. It's super boring to see です and ます most of the time, with occasional new grammar points thrown in. It's also strange that Duolingo introduces honorifics without context. This is super confusing. Who in the world would decipher a long string of characters out of a few really bland sentences?