Recommendations for trans fluid??

I remember taking my car back to my trans guy to remove and fix the mistake his guy made, putting the wrong shaft in the a-995 gear set I gave him to put in. When he saw the fancy blue trans fluid I put in, he just laughed and poured it down the drain. He said simply, “trans fluid is trans fluid, you don’t need that ****”. He should know, he’s been doing transmissions for almost 50 years, and everybody in my area goes to him, or went to him. He just retired and went off the grid. He never was much for people!
Yup, all the old school builders around here laugh at everyone wasting money on something that makes no difference. But thats cars for you.