What I don't understand, is why it's okay to cast black actors in a film or a play, but not to "play" a part in a themed area.
I think the easiest way I can attempt to explain it would be; Phantasialand don't employ black people to
only work in Deep in Africa, but Deep in Africa is the
only area that
only features black staff members. Phantasialand don't ensure that the Berlin area is staffed by natives from the Brandenburg region, nor do the Chinese or Mexican areas feature only Asian or South American workers. If you work on Mystery Castle, you are asked to wear a lab coat, you're not asked to don a prosthetic nose to resemble a wizard's assistant or whatever.
When you're a black actor in a play or a film, regardless of whether your race affects the role or not, you're performing, literally acting, for a brief period of time. When you work in Deep in Africa at Phantasialand, you are undertaking all sorts of menial, minimum-wage tasks associated with a theme park; checking restraints, cleaning up gum, measuring the heights of children disappointed to be several inches under 1.4m, then perhaps dealing with their angry parents. So you're dealing with all this crap, and all the while, people are literally seeing you as a subtle novelty, along with the thatched roofs or plastic snakes.
From what I understand, when you're black in a largely white country, you are already seen as 'different', and you feel that difference in subtle ways all of the time. This isn't always nefarious, in fact some people find it something to celebrate. When Phantasialand hire an all-black staff for their cartoonish (if not detailed!) Africa land, it lends itself to a tacky history of blackface, 'othering', etc. It just feels increasingly weird and inappropriate, to me at least.