My first instinct was to say that you're wrong because I'm very fond of Duolingo but I've also noticed that recently. I used to use Duolingo much more when it first came out and when it still was challenging. I actually had to think a little to get the answers right and I would make mistakes.
I've recently tried to practice Mandarin on Duolingo and it was a different experience. It just felt too easy - like Duolingo was trying to make sure I never leave my comfort zone and don't make any mistakes. And yeah, it was kind of boring so I stopped.
This has been a trend with video games for many years now.