Most apps focus too much on impeccable grammar (even if they usually restrict you to a few tenses/moods) and rote, non-contextual vocabulary learning. Both are, well, useless. Having perfect grammar but not knowing when to use which verb in which context won't get you far. It's like trying to learn how to code in some programming language by studying the formal syntax and rote memorizing a bunch of core functions from the standard library. You miss out on everything that actually makes a language.
All in all, it feels like this post was written by someone who mainly communicates (or learns to communicate) in foreign in writing.
> Forget intonation if it’s not entirely necessary. Especially in French, there is no need to learn if a word takes a ` or ‘.
I can't let that one go, sorry. You don't need to learn perfect spelling, but it's going to be obvious most of the time if it's é or è when you hear the word. And if you pronounce it weird, you will get confused looks. In English, do you "need" to learn if a word takes "o" or "u"? People who were raised with certain native languages cannot even hear the difference anyway, so why bother, I guess? I hope this makes my point clear.