Celebrity cameos are a problem if they take you out of the story, so that you are thinking "Oh, here's a crass appeal to popular culture." The last few seasons of Game of Thrones had plenty of narrative problems, but the Ed Sheeran cameo just screamed that the show no longer really cared about being taken seriously as a story. That property, like the Mandalorian, depends on being an entirely separate world than our own.
On the other hand, if a story is meant to be taken less seriously, then celebrity cameos can be a lot of fun. I loved the one in D&D:HaT because it was basically another good gag in a film that is all about good gags. When you've got a shaggy dog story to begin with, cameo away. But these cameos felt like they were undermining, not enhancing.