Why so critical of "universal" flex radiator hoses?

They're universal pieces of **** that don't flow worth a **** and don't mount worth a ****. They're designed to look perfectly at home on any car being driven to it's final resting place in the front yard of a mobile home, and sculpted to stand out as a purchase made by someone lacking enough self respect or taste to do the job right.
They're handy for installing aftermarket radiators because you're going to need to install double the cooling capacity in your $200 part to compensate for the lack of flow in your kinked up, half degraded rubber, Tijuana $10 part.

You would be better off to hire a Mexican to sit under the hood and transfer coolant from water pump to radiator and back with a five gallon bucket.

If it wasn't good enough for Ma Mopar, don't bother asking why it isn't good enough for you, unless you just really enjoy asking people for tows in the middle of the night.