>missing :WaitForChild()

That's good... isn't it?

It's not the end of the world, it's a minor convenience and better than busy waiting.

There are plenty of cases where you want to manipulate an object but it's not guaranteed that it exists before your code is run. You get similar functionality with:

while not parentObj:FindFirstChild("childObj name") do wait() end

AFAIK, wait() is >= 1/30 of a second, if you wanted to be extra timely you'd instead run every heartbeat.