I chose GS because I like the civs overall and I do appreciate the fact that FXS made the mid to late game better. Civs like Maori, Sweden, Inca, Phoenicia, Canada, Hungary, have all provided me interesting and fun games.
R+F I'm mixed because I love loyalty and governors, and game mechanic wise, this is probably the best expansion, but I really hate the civs. By far they are the worst in this game. There's a special place in hell for the dev who came up with the "If declare X war, Y for 10 turns" idea. Even if you ignore that you have super boring Korea or poor Mapuche which is a complete mess of a civ. So despite the game mechanics being more relevant than GS, the civs being so bad just brings it down.
DLC is pretty cheesy. Macedon and Australia are so boring because they are OP. Then you have Khmer who can actually be pretty fun, but their underpowered design sets them back. Indonesia is pretty great though.
NFP... Yeah let's just throw everything to the wall and see what sticks. Overall, it's been a letdown with a few really cool things here and there. I'll give FXS a break though because I know they're just testing out future features for Civ 7. And to their credit, they did make Ethiopia which is my favorite civ in all of Civ 6, so there's that.