Well, consider the origin of that comment. Dunno if it's in the book, but from the movie: Boromir: One does not simply walk into Mordor. Its black gates are guarded by more than just orcs. There is evil there that does not sleep, and the Great Eye is ever watchful. It is a barren wasteland, riddled with fire and ash and dust, the very air you breathe is a poisonous fume. Not with ten thousand men could you do this. It is folly.
High-profile entry is dismissed as impractical/unlikely/impossible. Sauron has, without doubt, considered and mitigated the obvious - including, we may presume, the obvious threats of Eagles entering for various purposes. Considering various obvious options for a few days will surely be inadequate against someone of immense power having considered defenses against assault for centuries. (Akin to my problem with people who think, with a mere few minutes of untrained thought, they can outwit teams of experienced professionals operating on near-unlimited budgets.) Just because a sold reason for "it can't happen" can't be imagined in a short time doesn't mean there isn't a reason. The defending force has capabilities beyond what is known (even to omniscient readers), the risk of failing to discern and mitigate a flaw in the plan is substantial, and the cost of failure is extreme. A flying attack (which taking The Ring to Mt Doom in effect is) is just too obvious for Sauron to have not considered and prepared against.
Frodo is chosen precisely because he is as low-profile as possible: a nobody, barely 3 feet high, moving at a paltry pace, not strong enough to wield the ring.
"Well, we can't think of a good reason not to, so let's do it" is not a winning strategy. If you can't qualify & quantify the risk, you don't take it. They could evaluate the risks with Frodo, and chose to engage in asymmetric warfare.
> riddled with fire and ash and dust, the very air you breathe is a poisonous fume
As carbon monoxide is lighter than air, orcs and other creatures on the ground are less affected and probably more adapted to the poisonous atmosphere of Mordor; whereas the eagles flying high and accustomed to the clean air of Middle Earth would simply succumb to the prolonged exposure to CO. Of course, the destruction of Mt. Doom and subsequent paralysis of Sauron's military capabilities allow the eagles to fly in at much lower altitudes in the end.
High-profile entry is dismissed as impractical/unlikely/impossible. Sauron has, without doubt, considered and mitigated the obvious - including, we may presume, the obvious threats of Eagles entering for various purposes. Considering various obvious options for a few days will surely be inadequate against someone of immense power having considered defenses against assault for centuries. (Akin to my problem with people who think, with a mere few minutes of untrained thought, they can outwit teams of experienced professionals operating on near-unlimited budgets.) Just because a sold reason for "it can't happen" can't be imagined in a short time doesn't mean there isn't a reason. The defending force has capabilities beyond what is known (even to omniscient readers), the risk of failing to discern and mitigate a flaw in the plan is substantial, and the cost of failure is extreme. A flying attack (which taking The Ring to Mt Doom in effect is) is just too obvious for Sauron to have not considered and prepared against.
Frodo is chosen precisely because he is as low-profile as possible: a nobody, barely 3 feet high, moving at a paltry pace, not strong enough to wield the ring.
"Well, we can't think of a good reason not to, so let's do it" is not a winning strategy. If you can't qualify & quantify the risk, you don't take it. They could evaluate the risks with Frodo, and chose to engage in asymmetric warfare.