I agree with you. A prime example of that type of casting can be found in old Shirly Temple movies. I forget the name of the man and woman but a black couple is talking and spelling words so Shirly can't hear and they mispell them badly. In truth both of the actors had college degrees but the best parts they could get were of menials and servants, always subservient to whites( I am white BTW). The blacks of the time had their own movie makers and while they would play in white films and be cast as servants, they would play the main charcters and heros in the black films. It was a racist time, no doubt.