SideshowGunboats are not a game-changing unlock because you can go around speedshotting and treating things like a jump map.
They're a game-changing unlock because they make every normal rocket-jump far less damaging, letting you jump without being tethered to a medic and letting you move around the map more quickly. It's not an unlock that you have to be skillful to use.
Being good for the game isn't the same as being a well designed weapon tho. Gunboats are well designed AND add to the game. Just because the Booties are a bad weapon doesn't mean they're bad for the game. Something can be OP (EP) or niche af (Conch) and still make the game more fun and interesting, but the idea should be to make weapons that both expand what the class can do with skill and allow the class to close holes in the game that are causing stalemates or unpleasant gameplay. Obviously not every weapon fits both criteria, the Basher isn't a hard weapon to use, and the winger doesn't change the game significantly, but hitting at least one of those is really important in making a weapon that works for 6s
Booties don't create a shift in the demoman class the way the gunboats do. They're not game-changing, and that's strike 1. Strike 2 is they're overpowered. 3 is they're less skill indexed and lower the skill ceiling of the class. Sorry that I didn't really complete that thought earlier but it was mostly a response to like a 3 month old post talking about them being shitty weapons, not shitty for the game.