The Amazon produces a lot of oxygen which is no surprise, it’s a lot of plants! But that isn’t the reason why we should care that it’s being burnt down. Most of our oxygen comes from water and is already in the atmosphere so the forest’s destruction isn’t going to impact that but it’s STILL a problem.
Science is a very cool thing but it’s complex. Most people think of oxygen as the stuff that comes from plants and we breathe it as they make it. That’s not incorrect, it does come from plant life but the short of it is, all the oxygen we breathe is in the air already and a forest burning down, even one as large as the Amazon, does not affect that.
But it does affect biodiversity in the world and it’s important that we keep that because once these places are gone and the life they hold, they aren’t coming back. We’re not going to start having to buy air like some science fiction movie but there’s more than enough reason to be appalled by what is happening.