It's true though. White goes from having a slight opening advantage to having to prove that he deserves to be alive. 2.Nf3 is of course a better move, as is 2.Nc3
the King's Gambit is a mistake

People abandon openings long before there is a forced win for one side. The King's Gambit is almost certainly a draw, but like many opening gambits White has to hang on in the ass end of an endgame in the critical lines.

Nigel Short (well I think it was him) said that the kings gambit was the best opening for white since there are so many ways to refute it and when your opponent is deciding on which of these ways to refute it he should play, you end up winning on time!

It's kinda weird. Center game (1. e4 e5 2.d4) is obviously inferior to the King's Gambit but the analysis engine says 2. d4 is good while 2. f4 is a mistake.
How is d4 inferior to f4?
The Centre Game (and Danish/Goring Gambit) is a lot less principled than the King's Gambit as it gives up control of the centre for no reason. In the King's Gambit Accepted however black is forced to capture away from the centre.

The Centre Game (and Danish/Goring Gambit) is a lot less principled than the King's Gambit as it gives up control of the centre for no reason. In the King's Gambit Accepted however black is forced to capture away from the centre.
Except that after 2 d4 exd4 the pawn can be regained at once, whereas after 2 f4 exf4 White isn't guaranteed to get it back at all. Effectively, the King's Gambit loses a pawn, so the site is probably justified in calling 2 f4 a mistake, though the fact that it did so still amuses me
King gambit is probably losing in centaur chess.
It may not be losing, but it's just not the sort of opening well suited for centaur chess perhaps? When looking at some of the correspondence games strong players appear to prefer closed and blocked positions in order for the human input to become more relevant, though I'm just speculating. For instance I recently saw a top game on ICCF in which the Stonewall structure was being played

there is no right opening ,engine itself often play king's gambit,and ofen play bishop before knight
I just finished a game and the site told me I'd made one mistake. I ran the analysis engine to see what it was, and it told me that (1 e4 e5) 2 f4 was a mistake. Lol