> It's a common issue: "I've got my entire tree gold, why can't I understand natives?"

As an alternative anecdote, I've been using Duolingo for years and spend some time in the forums + different Spanish learning communities whose users frequently use Duolingo and I have never seen anyone ever ask this.

It's always struck me as obvious to everyone that you would need multiple resources to become fluent, but Duolingo is useful as a good quality free resource that can be done anywhere at any time.

I'm not saying you're wrong, as we probably come across different posts or groups, just an another experience to share.