so itsa bad opening?
Well depending on how you play, any opening can be "bad." But from what FM Bluebird said, it is not a bad opening.
Nothing is so 'bad' in chess.
Depends how you play it!
The problem with asking such a question is that you have to understand that the term "King's Gambit" is only a generic title that covers 2 moves for white and one for black. I think in another thread on the King's Gambit I managed to name ten plus separate gambits stemming from this generic title after a black second move of 2...exf4. I would be the first one to admit that some of these gambit ideas are not theoretically the best but a good number of them are at least playable given the right circumstance. I do really well in Blitz with 1.e4 e5 2.f4 exf4 3.Qf3.
To ask if the King’s Gambit is a bad opening is like asking If Humans are dangerous....
There is nothing wrong with KG. It is completely out of fashion at the moment at top level.
Well, not completely out of fashion.
Carlsen also played it last year in a blitz tournament, and has played it in slow time controls too.
Did Tomashevsky not read Fischer's bust?
Perhaps the GM's of the past 2 decades have collectively decided that it's not 'sporting' to play such an easy win for Black ... after all, there are more important things than winning chess games, even if that would make your professional career more successful.