I think the higher level advice is to always be doing at least 2 things for language learning. You get nice combos from the synergy, gives you more opportunities to recall info outside of the app/class, and just is generally more motivating.
Agreed, with the caveat that having one of those two sources be Duolingo is a waste. Pair Pimsleur with a grammar book and vocab cards, or an hour a week of italki, and you'd be using your time much better.
The first thing I tell people is to ditch it if they’re serious about learning a second language, and go pay $20/month for Pimsleur.