Duolingo is great as a beginning to language study but that’s all there is to it. If you have a 410 day Spanish streak it’s time to start reading Spanish children’s books or watching telenovelas or Narcos, anything but continuing with Duolingo.
Yeah I agree (sorry I edited the original post to essentially say this while you wrote the comment). I also took a semester of Spanish in college and Duolingo let me (barely) place into the second level class. I've also been watching Spanish media (Telemundo, Casa de Papel, Pasion de Gavilanes) and just started a Spanish meetup group to practice speaking.
What Duolingo has been best for is getting a baseline vocab and familiarity with the language. It also lets you stay fresh/keep making progress when you don't have time or mental effort to spend more than a few minutes a day.
Duolingo takes you 10 minutes a day. If it's the only thing you're doing, I agree it's not sufficient, but I disagree with stopping doing it - it has mechanisms to reinforce what you learned.
But what you’ve learned isn’t all that valuable from a language perspective. It doesn’t matter how well is reinforcing lessons of those lessons weren’t very valuable in the first place.