We (me and my teens) used Duolingo for a few years and.. didn't really get that far in actually being able to speak. It's kind of mind-blowing that they are the market leaders. In retrospect, I think of it more like an addictive language game and not really a good way to actually learn to speak.
Latest in a long line of scams for learning a language. Goes back to cassette tapes and records. The only good way is the natural way: immerse yourself in it.
While in general I do agree with you (it's how I learned Italian, Hebrew, and Thai) being on the ground for a year is cost-prohibitive for me right now, and unreasonable for kids under 16.
What I've been building, with the help of a few language teachers, is our best guess at a really good way of learning new languages from the comfort of your home. It's not ever going to be perfect, but it is pretty good (at least so far in testing within our small group), and very cost-effective.
If you're interested in funding it, I'm happy to go live in Japan for a year :)