>

I've been following the set since it started (being a Voynich Manuscript geek for decades) and own the keycaps. 
It looks exactly as you would think a decrepit antique book should look. Even the legends knock it out of the park by having the watercolory effect of the book illustrations.
I mean, it's fine to be disappointed (some still are on the Discord channel) if you bought it hoping for a 1:1 replication of a render, but it's well keeping in with the point and theme.
I don't know why you're disappointed. It reminds me of my family's heirloom mahjong set. >

People complaining about the color doesn't seem to get that it's meant to look like aged parchment paper, just like the freaking book. >

aged parchment paper and oxidized plastic are not the same color.   
These keycaps are verging on a custard yellow in person.