It seems to me that foreign language learning is an area where computer technology has clearly miserably fallen short of its potential.
Apps like Duolingo and Babel are nice, but they seem to me more oriented toward making the user feel good about making progress then about achieving mastery in any useful time frame.
Flashcard tools like Anki and Tinycards are nice, but they lack enough readily available content to be really useful. Anyone with the expertise and perspective to use these tools in a practical time frame to assemble a deck of the many thousands of words necessary to achieve mastery doesn't need the tools.
It should be possible, using relatively simple tools, for a person to immerse oneself virtually in language learning materials. It should be simple to choose a rate of exposure to material from trickle to firehose. It should be possible to see an estimate of time remaining to achieve functional fluency at the current rate of progress, no different from the progress bar you see when downloading files.
Instead, each individual is forced to cadge together learning materials, of varying quality, in dribs and drabs; and guess at ones progress.
There are plenty of full-time University foreign language teaching staff around the world, they should be able to collaborate in production of content for online learning tools.
Yet neither the sophistication nor the efficiency of foreign language learning seems to have improved much in my lifetime.