>I have always been under the impression that the only reason children learn languages faster than adults is because they don’t worry so much about how they would be perceived if they said the wrong thing, pronounced something wrongly etc.

To piggyback on this, as someone learning a language as an adult, one thing that frustrated me the most was the inverse of the phenomenon you described - adults trying to be too polite and not correcting me when I made some mistakes, as long as they could understand what I meant. As soon as I had made close friends and made it explicitly clear to them, that I would really appreciate them pointing out my mistakes, that's when my biggest learning leaps occurred.

This. The more polite/reserved the culture the harder it is to learn by example.

Do children learn languages quicker?

Obviously they learn their native language quick because of full immersion plus playing and talking is pretty much the only thing they have to do. For other languages, if they spend say 3 hours a week learning another language they'd probably be at the same level as an adult spending the same amount of time. And things like curiosity, feeling of relevancy etc. are going to be a bigger factor in speed of learning I reckon.

My kids at certain age (between 2-4 yo) picked up a lot of Spanish by simply watching youtube videos for 1-2 hours a day (their fav. cartoon at the time Pocoyo was in Spanish). Compared to my learning efforts it was definitely going much easier for them, especially since it was completely unstructured learning for them, they had to figure out the meaning based just on the visual context. They've also learned a lot of Italian at the same time by simply listening to my wife's family talk between themselves (I listened them too, but my Italian still sucks). Problem is that they also forget most of it very quickly around 5 y/o (I guess it matches the period of infantile amnesia) unless they're exposed to the language regularly. So now they still understand Italian very good, but as they've lost interest in that cartoon they've quickly forgot most of their Spanish vocabulary.

When I first started learning French, I watched videos intended for French kids and I picked up a lot quickly. The biggest problem for me was, unlike a kid, I couldn't stand to watch them for very long. As an adult, boredom set in pretty quickly and thus loss of focus. However, it was still very useful until I got to a level where I could understand more adult content. It was certainly more useful than most traditional language learning materials.

> because they don’t worry so much about how they would be perceived

You can make the argument that this is the difference between being an adult and someone who is still a child.

That being said, it is not a black and white line, depending on the context many adults can act like children and many children can act like adults.