They are doing a TV show. The work has to be changed because of the medium and there are a lot of filler in the books that wouldn't work to cover 1:1. So it is silly to call changes only arrogance when they have to make the story work for the format. Not to mention they are telling a story based on hints and suggestions from Tolkien so it isn't "improving" but adding.
Dues Ex Machina isn't frowned on or avoided. It is only instances that are properly integrated with in the story that are a problem. The low effort things. Like I said Tolkien uses these same things you keep saying are bad for mature fantasy while at the same time crafting them in a way where it isn't a big deal that they appear. Like the river flooding to stop the Nazgul. It is a example of DEM (or at least "plot armor") but fits well enough in the setting to not be a bad thing.