I put my feet on the bulkhead. I try to book bulkhead seats so I can do this. It's very comfortable for me. (Rubber-soled shoes are best because they have a high coefficient of friction.)

I keep my shoes on (or use the socks from an amenity kit) because my feet are too clean to touch this type of surface. It's carpeted.

I don't understand why if you object to feet up on the bulkhead, you don't also have a problem with flat bed seats. With flat bed seats, feet are elevated and touching a surface as well.