Many people may not remember the "tablet revolution" of this period. Tons of consultants all raced to own and carry these things. They ran windows and worked fine but it just wasn't their time.
First of all if you are going to talk about valuation then that should be included here. And Google has always been terrible at developing and managing products. The list is too long to begin writing down. One funny example is the Pixel. I had a meeting with a slew of Google managers regarding mobile strategy (maps, reservations) and every single one of them had an iPhone. I doubt any of them ever even tried a Pixel. Same with the dozens (hundreds?) of software products that have died off or languished over the past 20 years.
Duolingo is already cash flow positive and if you back out some non-cash costs can say they are profitable. However some of these non-cash costs should be included but that's another story. Their target model is for 35% adjusted earnings margins which is aggressive. I did publish a post with our "present future value" model that goes out to 2026 and discounts things back. I only see them getting to 22% operating margins at this point but there are some areas like testing fees that could push that higher. Using the model I get to a $145 stock price that I'd say puts a full value on the next several years of growth. It's just a preliminary model now. After they report a few quarters we can put a finer point on it. Details here: https://ipocandy.com/2021/07/making-sense-of-duolingo-duol/
I feel the same way about Duolingo. I used to be able to speak a moderate amount of German and let it lapse. I picked up Duolingo because it substituted for some other casual activity I might do on my phone (crossword, read hackernews, etc.) And learning some conversational German feels like a better use of time. However it is pretty basic. I know there are hundreds or thousands of units and spending 10 minutes a day probably won't get me very far. Still if I keep it up and take a trip to German I'll at least know some of the basics. I practice with my long-suffering family who has to listen to me say Mein sohn is sehr klug! and other stuff like that all the time.