WMG / The Silmarillion

The Gift of Men is meaningless.
The whole point of the Gift of Men - i.e. free will - is to allow Humans to choose their fate freely. And yet Eru through Manwe is implied to lament men choosing to go their own way like Melkor, so what's the point of free will if men are simply supposed to go with the flow instead of making their own destiny and deciding for their own how the world should be, and not how it's meant to be?
  • The Gift of Men is not free will, it is Death, the ability of leaving this world forever instead of being permanently tied to it. Eru gave them free will, though. And the point of it is that men choose their own way... which they did. However, leaving your children freedom to make their own choices does not mean that you will not feel sad if you think that they are making a very, very wrong choice that will only bring them grief.
Ungoliath is actually It

Since Silmarillion doesn't confirm her fate, she could have found a nice place for herself, devouring souls of children in the darkness. Now Stephen King's dislike of spiders comes out in the whole new light.

Before his defeat, Morgoth was working on creating functional Humongous Mecha.
In the texts of the Fall of Gondolin it is mentioned that Morgoth's army included dragon-shaped tanks ("On Maeglin's advice Morgoth had his smiths and sorcerers construct iron monsters in the likeness of dragons, which might cross difficult terrain and harbour legions of orcs to transport them safely across the open plain of Tumladen") and bombers ("flying machines with fire on their bellies"). Clearly the next step was creating giant robots -like a Mazinger or a Gundam- or another kind of giant mechanical beasts. Good thing that the Valinor army struck as he was stuck on creating winged dragons.
If the Silmarillion is ever adapted for the silver screen, Benedict Cumberbatch will cameo as a Maia of Yavanna just returned from the far Harad or the Yellow Mountains.
"Aiwendil, my friend, you'll be glad to learn that your peng-wings are flourishing"
Eru hates Humans.
Out of all the races of Middle-Earth, humans are the weakest, the shortest-lived, and there doesn't seem to be much of anything they can do that either the Elves, Dwarves, or both can't do better — and that's without the whole "Gift" of Men. Yeah, yeah, supposedly death is a gift, but the ability to die is not the same the inevitability; a gift isn't really a gift if you have no choice but to accept it. Add in the fact that those who live a comparatively long life spend at least part of it old and infirm, and it doesn't seem like much of a gift at all. For all humans are supposedly special, in many ways they seem to have got the shaft compared to, well, everyone else.
  • Death is only part of the gift of Men. Men also have the unique ability to conceive of things not in the song of creation, while Elves are bound to it (and how Dwarves fit in is unknown). I generally take this to mean that since Middle-Earth is supposed to be our own world, our modern, non-magical advancements are a result of our ability to think in ways that other races can't.
Ungoliant was made of neutron or even quark star matter.
Ungoliant is described as descending from the darkness above Arda. That could have meant she was a meteorite. She is mentioned to have an all-devouring hunger, which could have been due to gravitational pull (then why she didn't simply burrow into the ground could bbe explained only by Arda being flat at the time). After she absorbed the two trees, she grew in size and started letting out a cloud of Unlight which could not be penetrated and actively drained light. Perhaps she reached critical mass? It could be that she was concealed by a gravitational lensing effect. Then she died by dissipating via Hawking radiation after she migrated South. Of course, all this leaves every event where her body interacts with anything (ground, enemies, Melkor, trees, Silmarils, her own limbs) unexplainable.