I speak 3 languages, attempted to learn the 4th one (German) on Duolingo and I find it very ineffective.
I recall having trouble learning English back in high school and then having a breakthrough. The breakthrough was, I figured out how to think in English when trying to debug my errors with the teacher who actually have lived in the USA. Once it clicked, I no longer had to memorise things but predict instead. My English is still not perfect but I can have fluent conversations and almost never need to look up words, I can figure out the meaning of idioms etc.
IMHO, the gamification in Duolingo is not geared towards making you figure out the mechanics behind the language. I think edge case exploration is way to go but the gamification usually revolves around memorising.
I agree. One skill is recognizing the meaning from a sentence already formed (what Duolingo puzzles consist of). A very different skill is coming up with the sentence in the target language without hints.
There is the company called Assimil that has small books based on this concept, where first you are filling in the blanks (not choose from preexisting options) and as the book progresses you have to fill in more and more of the sentence.
This heavily depends on a course, and courses are different between pairs of languages.
E.g. learning Spanish from English on Duolingo is very natural, the course is built the way a baby learns a language, by practice and suggestion, with few small bits of grammar info strewn along the way. According to reports from my friends, learning Spanish from Russian on Duolingo is a completely different experience, all based on memorizing large amounts of rules before any practice even begins, and it works really poorly.
I assume that learning languages on Duolingo is all about building a chain of good courses based on languages you already know by the moment you consider another one. (Only partly joking.)
Duolingo is a pretty good tool for practice, but for trying to learn a language from scratch it's probably best to go through some YouTube videos for the pronunciation and some books first and consider it a kind of fancy flash card thing to do on the side.
For my young kids ( under 10 ), I am very strict on what they can see and do online. Screen time, CleanBrowsing, and app restrictions enabled.
For my teenager, it is a bit different. More conversation, more privacy and more spending time teaching her about computers, security, privacy, etc. She chose to install CleanBrowsing, an ad blocker, all on her own to protect herself.
It depends on the reason to learn a new language. Once you know a few languages, you generally only learn a new one if you are trying to solve a specific problem that it can do better.
What I try is to solve a small piece of the problem I am trying to solve to get more familiar with it before committing.