I fundamentally disagree. There might be problems that require ironing out, to be sure (remember that these press builds were more than a month old prior to the Lets Play videos being released) but Civ6 diplomacy actually appears to combine the best elements of Civ4 and Civ5 diplomacy, with a nice bit of Cassus Belli thrown in for good measure.
I like the fact that aspects of your diplomatic relations are initially hidden, as it forces you to pay more attention to forming closer bonds with these civs (or spying on them).
My only hope is that, in upcoming expansions and/or DLC we will see a return of the concept of State Religion playing a role in early game diplomacy (beyond certain agendas)......a la Civ4. Though I hope its not as instantly overwhelming as it was in Civ4

.