I was disappointed to see a lack of Gaul fans. The New Frontier Pass has been very inconsistent with how good the civilizations are, so I am hoping they design Portugal well. Byzantium is my least favorite so far since it has a lot of wasted potential, followed by Babylon which i am still conflicted about, though I was still surprised to see not that many people liked it relatively speaking as a large portion of the community seemed to react positively to it. I despite the leader design and the Eurekas are very gimmicky. Gran Colombia might be my 3rd least favorite for the NFP followed by the Maya due to their very wonky start conditions
The final update with Portugal will make or break the NFP for me
I'm generally pretty fond of the NFP all things considered.
Maya: I think the Civ is pretty underpowered and there's a lot of little things that make them frustrating to play, even if their bonuses were good. But the core idea behind the Maya I really like, and I wish there were more Civs that broke the mold like they did. If they had a few quality of life improvements, not even necessarily buffs, I'd say they're one of the better designed Civs in the game. A Civ doesn't have to be crazy overpowered to be well-designed (post-rework Norway is a great example of this).
Gran Colombia: I feel weird about this Civ because they're very fun to play, but at the same time they feel somewhat uninspired. They're mostly carried by the movement bonus, which while very fun to break the game with, it's also pretty bland when you take a step back from it.
Ethiopia: Everything about this Civ intersects with each other in a meaningful way, meaning from a design perspective this Civ is very well-thought-out. That being said, I personally find them boring to play, but that's just personal taste speaking.
Byzantium: Sort of a one-trick pony (or maybe two-trick pony that uses the same strategy), but that one trick is very fun. I don't see myself revisiting Byzantium that often, but the game I had with them was quite enjoyable.
Gaul: I really do love this design, as it takes a lot of the conventions you'd expect from a Civ and flip them on their heads. They're uniquely strong in a really generalist way, meaning just about any playstyle can work for them. One of the best designs in the pass, and really in the game.
Babylon: I love how stupid this Civ is. They pretty much break the game, which while makes for a breeze of a game, it also gives you a unique gameplay experience you can't find anywhere else. That said, the early game for Babylon is a drag, which I'm not as fond of. I have a love/hate relationship with Hammurabi.
Vietnam: Definitely one of the more inspired Civs in the pass, along with the Maya and Gaul. I really like how their ability interacts with the environment, which is one of the main draws of Civ VI in general--making the most out of your tiles. Playing a cultural turtle is fun, and they're a better expression of that than the Mapuche I feel. The conversion of the Encampment into a district that also helps you in a Culture Victory is pretty unique too. I like them a lot.
Kublai Khan: On one hand, I do like how the ability plays off the different uniques of China and Mongolia in different ways; it's a better expression of the multi-Civ leader than Eleanor is, in my opinion. On the other hand, Kublai sort of has Simon Bolivar syndrome: the ability's pretty powerful, but somewhat boring. Part of me also wishes that we could have a different, more Chinese alternate leader for the Middle Kingdom, but Kublai Khan is a big personality so I'm somewhat ok with it (that's also off-topic for this thread, but I just wanted to put that out there).
All things considered, most of these Civs I have pretty positive impressions of. The ones that I'm less fond of aren't even poorly designed, but just ones I kind of find boring. I think by this Pass (and to a lesser extent, Gathering Storm), the devs really got a feel of what kind of bonuses capitalize the most off of Civ VI's systems, and put together some really banger designs.