Back in July, I made it to the Diamond League in Duolingo, and it was only semi-ironically that I declared it my major accomplishment for the year. 2020: take your wins where you could get them, I say.
Many days later—308 "consecutive" days, although there are a few streak freeze days in there—I finished the Chinese course:

Please clap.
OK, simmer down.
When I started using Duolingo in 2013, there wasn't even a Chinese course. I mostly did the Spanish course (to better understand the local language in California) with a little bit of Portuguese (since our main customer at Mason was Embraer down in Brazil).
Duolingo works well for me because it is a game—it reaches right into that part of my brain that counts points and acknowledges streaks even though they're meaningless. You don't win anything, but you have many of the ceremonies of advancing in tournaments and winning. Even much of the content itself has limited educational value—but it has some value, so if you keep going, you get something out of it. The language content isn't optimal—whatever "optimal" might mean here, I'm not very concerned about defining—but your knowledge will follow an upward trend.
Duolingo is dessert. You can't (shouldn't) live off it, but it is nice and good and has its place in the world and I'm not going to stop eating it.
I've been thinking of bailing out of the Duolingo Chinese course for ages now, but more than wanting to finish the course for its content, I believed in the value of sticking to something to the end because my self-education history is a scrapyard of partially-finished projects. It's a weakness of mine to have some other plan catch my attention before the finish line, and then run after that; then another one, then run there; then another and run; and so on and so on. (Bokonon: "Round and round and round we spin, / With feet of lead and wings of tin".)
So: I stuck this one out. Now what?
On Duolingo? I don't know. I think it could come in handy to study the language for places where I'm planning to travel, if the language is available. I think the app is good for languages you don't plan to master, but just want to learn a bit about. The other languages aren't my focus, though.
Chinese? See, this one I want to master, so I have to figure out the next path. A simple, discrete goal for this year is to get up to HSK Level 4. A certification like that is a lot of vocabulary and grammar patterns—useful stuff, but in and of itself not very interesting. I don't care about a certification, but it is a landmark off in the distance that I can walk toward. Not not-moving is key.
It would be more interesting to be able to read good literature in Chinese. It would be more interesting to understand what the crosstalk performers are joking about. It would be more interesting to be able to both understand what people are saying to me and say something back to them—not just something but something witty and hilarious. (The people of the Chinese-speaking world deserve this Content and I must not deprive them of it.)
So I'll make a new path. I don't know what it is yet, but I'll head off in some direction, then adapt and adapt and adapt. It's a little bit like hiking. Sometimes it's best to know exactly where you want to go and how to get there. Sometimes it's even better to have a rough idea of where to go, no idea how to get there, and then have an open-ended adventure as you find or don't find a destination. I've found some places in India and Inyo County and Ingersoll Scout Reservation that have stuck in my memories all these years, and I don't know where they are, what they are, or how I got there. It's a matter of taste to decide which type of trip to take when it's time to set out, and then again when you're out there, and then again when you've returned.