if you need mechanics to do social ROLE playing you need to think outside the box. D&D very much has the chops for social interaction etc. and we did it for years without a skill system even.Yeah, but a lot of planetary romance is about social interactions with new and weird cultures, politics, and the like.
Frank Herbert's Dune should qualify as a planetary romance, for example. As does Robert Silverberg's Majipoor series, Philip Jose Farmer's Riverworld, and C.S. Lewis' Space Trilogy. Most of which are dominated by social interaction, not combat.
So, the point about D&D not having the mechanical chops still holds.