Fantasy vs. Science Fiction

Okay, if a dragon's hide deflects magic, energy, bullets, projectiles, doesn't get wet in the rain, and protects against heat and cold, then, I repeat, why is a dragon killed by some pathetic Knight with a simple sword in his hand?

Bullets simply won't penetrate, and it's hard to hit with a projectile.
This Knight (just one?! Well, well... even logically, you can figure it out...) is holding a sword made of an unknown metal and, again, with unknown enchantments.
This isn't pure magic; it's a way of giving the sword certain properties.

otherwise, they wouldn't be able to move, let alone fly.

No one said that a dragon's hide is a solid frame. It's scales.
Why do they need feathers? Bats don't have them either, and they fly.
They are supported in the air by incredible strength.
And why couldn't magic support them?

reptiles are like that.

Reptiles are like that.
Dragons are dragons. They are not cold-blooded.

if you insist on this, imagine that a blaster hits a pumpkin, inflicting injuries to the head of the poor lizard. And if it doesn't hit, it ignites the air, which quickly burns out, and the dragon has nothing to breathe. Or the fire penetrates the lungs and esophagus. I doubt that if a dragon breathes air calmly, the furnace is not a separate organ, which means that inhaling hot air is, let's say, unpleasant.

I'm not insisting. The dragon has nothing to breathe? How powerful must the blaster be to burn so much air? Where will you get a metal for a weapon that won't melt when fired?
To exhale fire, you need a lot of air. A dragon can provide itself with air for breathing for a long time by sacrificing the air intended for flames.
I don't think the dragon will suffer much from hot air after exhaling flames; the air isn't particularly cool then either.

some Inquisitors can perform Exterminatus.

Is this magic?

I doubt it's faster than even a military helicopter.

No one has seen what they are capable of. And if a ship needs to overcome various physical obstacles, then a dragon that can cast teleport has to overcome something greater...

nonsense, a huge ship will simply aim its guns, but the dragon will try to escape from them if it's not stupid.

Nevertheless, it will be funny to see a ship firing all its guns at a single dragon.

in the end, the long-suffering Smog was killed by a single arrow that hit him in the belly. There is no super-imba scale on their belly.

1. This single arrow was very unusual. Don't tell me...
2. Smog had a hole in his belly... 2x2 cm. It's all about accuracy.

How can dragons be invulnerable if weaker units, almost in packs, kill them?

In what ratio? And nothing is known about the nature of these units.
Cheers :)

What does magical energy have to do with it?

Isn't a blaster energy?

These are just your assumptions and stretches based on your personal sympathy for dragons. Saying that a dragon cannot be killed by a blaster or a rocket is just nonsense.

I am providing arguments. Where are yours now? :)

Yes, the dragons of Arkata are fire elementals. Or do they also have diamond scales that are impenetrable?

They are made of fire. Creations of fire. It will be difficult to destroy fire with fire. And they clearly can't be extinguished with water.
If you give a cyborg a sword and put him in armor, he won't do anything to an Arkata Dragon, but Knights can compete. So, they are not ordinary.

A fighter will fire from a ship's gun, which will pierce the hide of any dragon. So, at least several dragons can be shot down. And by the way, the armor of the same fighter is not a knight's armor.

What does it mean, a fighter will fire? Charge and send it straight? How to hit?
Not armor. However, Knights clearly don't have ordinary armor either.