And (admittedly maybe by design) it ignores the real important part of citizenship, which is the residence rights to your home country and beyond when you're not traveling the world. The city-state of Singapore is nice, but a French passport holder's right to live in any EU country is fantastic.

Edit: Searching around, this (2018) is exactly what I had in mind--travel freedom + settlement freedom: https://www.nationalityindex.com/