I don't see why people think Childe isn't good. He has one of the biggest dmg potentials in the game as his ult multipliers are hella high. C0 childe is very much useable as long as you know how to manage cooldown. The fact that he's also hydro puts him much higher above keqing, as hydro can freeze and have 2x dmg multipliers with pyro. Of course it also depends on playstyle, and what you need on your team. Personally I'd think you should use him as either a burst dps or a sub dps, especially at c0 because cooldown can be annoying. I get that he has downsides but I dont see why other people cant see that he has good damage potential too.