I'd like to add another problem there: there was no such thing as a <bleep>ing catapult at the time.
The first siege engines ever were the ladders and battering ram, the former being pretty much as old as there was a wall, and the latter being discovered by the Assyrians. One of the earliest images of a battering ram is actually as late as 9'th century BCE, so yeah, even that idea didn't happen very early. (The Romans, cf Vitruvius, actually attribute the first battering ram to a Carthaginian engineer, so, yeah, 1'st millennium BCE anyway.)
The catapult, or more accurately an onager type one, is first used by the Greeks, somewhere mid 1'st millennium BCE. But it's slow to spread even in Greece, with most city assault battles involving no more than ladders. Even battering rams are first confirmed in the west in 503 BC or so when the Romans use them against the Arunci, and Greeks first use them as late as Platea in 427 BC. Catapults spread even later.
Which, among other things, tells us that the Egyptians didn't have catapults either, THAT late, since the Greeks were certifiable fanboys of the Egyptians.
So aside from the size and structurally rigidity problems, which dasmiller already calculated, the problem with a catapult-launched glider at the time was that there was no <bleep>ing catapult to launch it. It's the kind of nonsense that can only come from and appeal to idiots for whom "ancient" (or for that matter, "medieval") are some uniform mix of everything across thousands of years, and who aren't even vaguely aware that there was a timeline of such inventions.
I included the word inertia to cover your entire post. The inertia from the launch, then gravity, are what moves a glider along.
