Wrong.
There's multiple reasons why an aio is loud, not simply due to it being bunk. If there is air trapped in the pump, it'll be loud, simple fix is tilt the pc while running so the radiator is @45° or better above the lowest point of tubing or pump.
Also, Op does not mention exactly what is loud, the fans or the pump, it could very well be as simple as the pwm fans are set on an uncontrolled header, so there's no choice but full 12v fan speeds or the bios is set to use analog for system fans, so there's no pwm signal, or if there is any software control over the fans at all.
The largest by far contributor to any noise in an aio is a fan. Exactly the same as an air cooler. Crappy fans = noise, doesn't matter liquid or air. If Noctua made an aio, that'd shut everybody up about aios being loud. Some are loud, either defective pumps or crap fans, but if you'd ever dealt with the stock amd cpu cooler fans from the 90's, most aios are far quieter by a long shot.