The market gardener is awful.
It promotes a retarded soldier playstyle. Even if you suck with it, I constantly see soldiers running it in pugs, scrims, and matches and constantly going for spoons with it and feeding. Everyone is now using it because they see people like jay and nubbi using it, causing a constant feed soldier mentality in pugs which is annoying and can make playing medic/demo unfun. It's also infuriating when a soldier keeps high/fast bombing and dropping the med with the spoon, as there is literally nothing you can do to counter it besides hitting an insane airshot or hitting meatshots as a scout. He jumps so fast you can't even call to your medic/combo that he's bombing and having them react fast enough.
If you're a demoman, you can only really counter it by hitting an airshot or playing super passive. If you're a medic, good luck. If a soldier without the market gardener bombs you, you have a chance to surf or juke him (even if you don't see him at first), but if he has the market gardener, it's almost a guaranteed drop for free. And also, ping makes it seem like he's gonna miss you but he hits you 3 feet away, and melee hitboxes are broken in this game.
Obviously there are ways to counter the spoon, like awareness and movement, and it definitely is not overpowered, rather it is just a gimmick. But man is it infuriating when you almost wipe the enemy team, but the last remaining soldier jumps in and drops your medic with the spoon, and there's literally nothing you can do.
Edit: Also in a soldier v soldier, the soldier with the market gardener just has to strafe while the other person has to either go for a hard airshot or counterjump, and even when he counterjumps he can still get hit.