This is a solid game in its niche marked of 4x games, and more specifically, 4x games with space age human colonization. With its only direct competitor being the blatant AAA cash-in Civ: Beyond Earth, it is clear that this dev does not have much to compete against.
Let's start with the bad, because everyone else starts with the good, and I'm a unique and interesting individual, as well as a special snowflake, so I go out of my way to be different in ways that try to be clever but miss the mark entirely.
-Lack of diversity and depth
This has been said since the beginning, and it still applies. Units lack variety, game mechanics are simplistic, factions are flaccid copies of their Alpha Centauri counterparts, and buildings have few functions. The game replaces real depth and variety with gimmicks like the Messari Invasion and the Nashira Eclipse (both paid-for DLC, of course), which get old and tired quickly.
There are only a few types of military unit: Infantry, Scout Vehicle, Tank, Mech, Helicopter, Boat, and Artillery. All factions have the exact same units, with the exception of the Messari, who have their own units, and the aliens, who also have their own units. Units all have a linear upgrade path of three tiers, corresponding with the three epochs of the tech tree. These units have Attack, Defense, Rank, Movement, and Health stats. These stats are boosted by a linear path of weapon and armor equipment, as well as gadgets, which are not linear and each grant unique abilities to the unit. The narrow scope and linear progression limit gameplay options and make unit customization a chore rather than the fun and interesting experience it should be. It also makes war less interesting. There is also little reason to have any meaningful combined arms force. There is no bonus or strategic incentive to have a variety of different types of units. This means, in theory, if you have an army of only scout vehicles against an army of helicopters, infantry, tanks, and artillery, you will win given you have the numbers, which is not at all realistic or interesting.
There are three kinds of combat: direct attack, artillery strike, and orbital strike. You will have no meaningful use of air force (since the only air unit in the game functions the same as the ground units), unit supply/logistics, morale, or other such thing that would add depth and realism to warfare.
There seems to be absolutely no effort on the part of the developers to add real depth to the game as they clearly favor gimmicks that sound cool and people will buy just because they sound cool.
Diplomacy is very limited in this game. It very much comes down to agreeing not to attack each other, attacking each other, and open borders. Anything else is too hard to achieve or too useless to mention. People will complain that the AI puts too much emphasis on another faction's military power, but I have no problem with this, as it adds a competitive edge to the game as well as gives it some semblance of realism (let's be honest; when you have an ideology different from everyone else's and a ♥♥♥♥ poor military, even the Gaians would want to gobble you up.) However, I do agree that it is too simplistic in this regard. You get no sense of geopolitics, where the different factions would take into account supply and demand for resources, the layout of the land, etc. What you get is a sense that you're surrounded by countries each led by a schoolyard bully, and the only way to win is by being the biggest bully in the playground.
-Lack of mod tools/support
The devs champoined their use of the .xml format in making the game more customizable, but anyone who has attempted to mod this game will quickly discover that there is only so much you can do with them. You can change stats, you can add new techs, and other small things. But there is no way to change the UI, there is no way to make meshes/models for new units unless you have programming knowledge and patience for navigating the xml's mess of verticy coordinates, or other actually useful things if you're serious about modding. This game is not friendly to modding to any significant extent.
-Blatant cash milking
As mentioned above, depth is replaced by gimmicks. These gimmicks come in the form of DLC that you pay for. They add nothing of substance to the game. The weak espionage system introduced in the latest expansion is also little more than a gimmick.
The game suffers from few bugs, and there is no game-breaking mechanic to make this unplayable. It's not the most fun, but it's not completely unplayable.
-Well designed atmosphere
The music, sound effects, art style, the factions, the alien life, all flow together fairly well. At first glance, it can actually be impressive. And even when that inevitable point in time comes when you get bored with it and it becomes old (because it does get old), it's at least not intolerable.
Unlike other games (*cough* Beyond Earth), this UI is informative and not invasive. Nothing is hidden from you. However, there is an issue with the game encyclopedia being limited to things that you've already discovered, which is frustrating for anyone who's done more than three playthroughs.
This game's selling point is that it's the spiritual successor to Alpha Centauri. It very much uses the reputation of Alpha Centauri as a crutch to keep it standing, rather than standing on its own merit, which is actually quite mediocre. And of course, the devs don't plan on doing anything about this. Aside from the devs' love of gimmicky DLC, they also love to handle a bunch of projects at the same time, ensuring that none of them get the TLC they need to be worth any significant amount of time or effort. After all, why stick to a game to make improvements and developments when you can crank out half-baked cool ideas and make more sales?