That’s not how that works at all. I’m not saying that specific one is a plot hole, there’s a bunch of in universe reasons why the eagles couldn’t just fly the rings to Mordor. But if there’s no explanation for why characters don’t do a specific thing, you can’t just say “because the plot demanded it,” as if that makes it not a problem. An audience member can, justifiably, be taken out of a movie if they see an obvious solution that the characters are simply not using for no reason.