That doesn't match my experience driving with no cooling fan at all. Ideling will overheat the engine, moving slowly like 15-25mph it stabilizes fairly well, and 35mph+ it cools and never gets any hotter than with the fan. I'd dare to say you have a dirty radiator, restricted coolant flow, or the vehicle is of a poor design.
Ages ago I remember some nascar driver saying they only need a radiator the size of a beer can to cool the engine while driving on the raceway. No stop and go traffic there.
My oldsmobile cutlass ciera was the same way too, I could hit the fan kick on because it was so out of balance. It also had the fuse blown when I got it, found out the fan didn't work when tuning the sound system (balancing the base and such) with the engine running. Every time I stopped for about 2 mins the cooling fan would kick on, but never while moving.
Of course there's always exceptions, like a rear engine vehicle I'm sure the cooling fan is 100% required since it doesn't have the frontal area.
If I did the math right, it's about 4840 CFM per sq ft of radiator at 55mph.
A quick search suggests this is one of the highest rated CFM fans for 16in (over 1 sq ft area) and it only pulls 3140 CFM. The radiator in every vehicle I've ever owned has been a lot larger than 1 sq ft, smallest I've seen is a geo metro and I'd guess it's like 1.5 sq ft.
https://www.becool.com/jump/fans
Assuming the fan is 16x16 square area, it's 1.78 sq ft. Same area with 55mph air would be 8615cfm. If I did the math correctly, the fan's ability to move air vs the natural air speed of traveling are roughly the same at 20mph.
Here's the source for the math I used, I reversed what they did since I'm starting with mph.
https://sciencing.com/how-8191327-ca...e-cfm-mph.html
It's very possible I got the math wrong, but I suspect it should be pretty close since that matches up with my experience. Of course the CFM of driving through the air will be a little less because of the air resistance through the radiator and it's not 100% exposed. even at 50% or the air going through the radiator, it would be 40mph+ a cooling fan can't keep up.