Lots of early physics was also not done very well, lots of fudges, etc. Does that discredit the idea of applying science to particle movements? Does Freud discredit the entire idea of psychiatry?

Physicists kept doing science, and it got better. Actual proper science has developed to the point where the computer I'm typing this on has a complex network of billions of logic gates which operates correctly billions of times a second. I can reasonably expect the CPU to continue to work for decades.

When managerial "scientists" can achieve anything even remotely comparable to that level of reliability and reproducibility, it will be time to take it seriously as a science. Until then, it just isn't one.

Many fields don't give that same level of reliability and reproducability; climate science, psychology and environmental engineering are all in the same boat. Guess none of them are sciences.