I hope he makes it a franchise.Star Trek is not supposed to be linked to any one era. It needs to always feel au courant so that it can continue to be extended with movies and TV series.
Forbidden Planet can be a nostalgia-fest because it isn't expected to be anything more than one movie. It's not a franchise.
Star Trek needs to be taken seriously by modern audiences to be continuously viable. Forbidden Planet can just be an ancient artifact and still make enough money for a single movie.
Also, we don't yet know if the retro look will get Forbidden Planet laughed off the screen. I think it should do okay, the "old-movie-look" gimmick has been used several times in movies, like that one with George Clooney and Cait Blanchett made to look like a Warner's Brothers' WWII era movie.