Yeah I heard a criticism of e.g. Duolingo the other day; even after two years on it daily, you'll know plenty of words and I suppose simple sentences, but you can't actually speak or comprehend the language, not unlike what the OP mentions.

I haven't learned a new language since high school, but I think to learn one you need immersion. Individual words for sure, but the focus should quickly go to reading whole sentences / paragraphs / books, listening to native speakers in their natural environment, and (probably the most difficult one to do on an app) speaking / conversation practice.

I only know English well because of daily exposure through media and twenty years of shitposting on the internet.

> (probably the most difficult one to do on an app) speaking / conversation practice.

Conversation practice with humans [0] is key: As a child I had complete, native-level fluency in French, because my first few years of school were in the local schools of a farm village in the interior of France (my US Air Force dad was stationed at a nearby air base). All through high school and college back in the U.S., I took French for the easy A. But now mumble years later, when my wife and I watch French TV shows on Netflix, I have to rely on the subtitles because I just can't keep up.

I've read comments by people from non-English-speaking countries who say they learned English by watching Friends on TV. I can't imagine how they did it.

[0] Maybe someday an AI could substitute for a human native speaker in conversation practice?

> I had good success with https://www.languagetransfer.org/

Yeah, I tend to think for the specific case of languages that share a common root, language transfer is unbeatable value (especially since it's entirely free).

I also didn't understand the point the authour was trying to make about this method being superior at allowing a learner to remember things under pressure.