So far my experience with Civ VI is that I played it twice, thought it was the best launch Firaxis has had in years and a decent game in its own right, but haven't touched it since, nor even thought about touching it. I don't know. It's not the complete wreck Civ V or BE were at launch, but it's just kinda... meh.
I feel like the difference is that as the 4X genre has seen something of a renaissance in the past five years or so, Civ doesn't hold the monopoly on the genre that it used to. I mean, Civ 1 and 2 had decent competition, but I feel like with Civ 3 and 4, and even 5 to an extent, there was kind of this "Love it or hate it, what else are you going to play?" (The answer being older games, obviously, but every once in a while you want to get something new in there). But I feel like there are so many recent 4X releases that I could be sinking my teeth into instead. To me, why would I play Civ 6 when Dominions 4, Age of Wonders 3, EU 4, Endless Legend, and others, all provide more enjoyable experiences? And that's to say nothing of the vast wealth of older 4X games. Honestly if a crazed terrorist were to say "I'll nuke the world if you don't stop playing Simtex games" then I guess everyone should probably say their last goodbyes now.
That being said, I understand Civ's appeal. It's a simple game to learn that offers an amalgam of playstyles. I think that Civ V's mechanics, while not the best in the series, did offer a degree of empire customization that was heretofore unseen, and I think that's kind of the direction the series as a whole is going to end up taking. Make your empire, your way, and become, in a way, the SimCity of 4Xs. Nothing wrong with that, and I understand the appeal. It's just not really what I'm looking for right now.
I am glad to see that Civ 6 is following Civ 5's lead when it comes to wonders. This might be a controversial statement (lol, "might") but I think these past two games have done wonders the best out of the entire series. The problem with wonders in Civ 1-4 is that the amount of hammers the wonder would take to build would often yield you an army large enough to capture the city where the wonder was held. Then you could build that army, take the city that built the wonder, and wind up having the wonder anyway, except now you've also got a new city in your empire, and your standing force is increased by whoever survived the invasion. Civ 5 and 6 have subverted this a bit by continually introducing wonders that provide a one-time bonus upon construction. It's still true that there are generally better things to spend hammers on, and wonder-whoring is often going to be a suboptimal strategy, but at least there's now some benefit to being the one who actually builds them.
(Obviously every Civ game (except maybe 1? I don't remember) has had at least one wonder that gives an immediate bonus - The Oracle or Darwin's Voyage or the like. But it's becoming more common).