Assuming the apps actually use native speaker audio. Which Duolingo doesn't do.

> I really don't think recommending textbooks is at all relevant these days.

I disagree completely. Textbooks are still, in my opinion and experience, the most efficient way to start learning a language.

> really you have to be pretty far along for grammar to be the main stumbling block (over listening, pronunciation, and vocabulary).

I wouldn't agree you have to be "pretty far along". Grammar becomes a huge stumbling block as soon as you get outside the pleasantries section of learning. Once you start trying to talk about your day and what you'll do and did, then the grammar really starts to matter.