My tools serve me, not the other way around. It’s not worth the time and effort to wash by hand or sharpen on a whetstone. I don’t need an expensive knife to cook at home. A pull through sharpener and honing steel are adequate. Get the right material and you don’t have to worry about the metal in the dishwasher.
How does a dishwasher dull a knife?
I run my steak knives through it all the time, they get sharpened 1/4 as often (or less, like 2x a year) as my hand washed chef’s knife, which could be sharpened every week (it’s a very good Henckels set).
It bounces it around from the jets of water.
There’s also abrasive in the detergent IIRC, but idk if that would make any appreciable difference.
Placebo problems created by hyperfocusing on one thing (knife sharpness) leading to bullshit flying around