There's a method of language learning - comprehensible input - that is basically this.

Though you need to start by watching/listening things you can actually understand. So start with Peppa Pig level, where they use basic vocabulary, repeat often, and use many visual aids, then work up to content for adults.

Trouble is finding enough learner level content to watch (without going insane). You need many hundreds of hours of content that you understand 90-95% of.

But even if you start with content way too advanced you'd be surprised what many hundreds of hours of listening to a language can do. Not efficient or recommended, but if they're ACTIVELY listening to the sounds of the language they could pick up a lot of meaning over such large amounts of time.