Yeah I get that. I don't think my son is ready for something effortful like LingQ. So, even if Duolingo is only a tenth as effective per unit of time spent, it's better than nothing.
We’ve seen excellent improvement with our son using Voiczy daily. Of course, we know we’re not perfect. We're just a small parent-run company. It’s just me, my partner, and our son, who happens to be our main tester! :)