It's because we had to jump back from Civilization 5, with two good expansions full of religion, politics, decent diplomacy (not great), a shit ton of options, the three modern era philosophies, multiple routes to win, assets that have obvious advantages and every turn, you had to handle six or seven different aspects of your Civilization so even if you're playing a more defensive, peaceful game, you've got Missionaries and Inquisitors, you've got Great People being born, you're dealing with City States, you're trading resources, you're picking out Social Policies, you're deciding your science, you're buying land and building settlers, you're handling trade and using Workers to build farms or such, and so on and so forth.
Here is why Beyond Earth is (currenty bad):
Beyond Earth has a crap setting.
Despite the most amazing opening cinematic in a long time, I don't give a crap. Most of the backgrounds barely matter in the game (we could have a part when, if you picked Nobles, you have an advisor you have to deal with who is a Noble who would push for more Culture or Economy, or if you picked the People, they want more cities and more health, or if you picked soldiers, they'll argue for more war or a bigger army or to fight the alien, etc) so no matter what you pick, you'll end up picking the Worker every single time because it's the clear best choice, and you'll pick the Love the Alien route because they force it down your throat and all good technologies force you to have it, plus it's so utterly overpowered. I don't know or care who any of the others are, they have no personality, your choices don't change very much each game.
Like was said above, the normal Civ game has real history. I say I'm the Romans, you know exactly what that means. I build the Great Wall, you already have a mental image. I say we start worshipping Islam, you've got another idea. I start following Facism, you know what that is. History makes up the window dressing of the main Civ line. Beyond Earth just didn't. At least Alpha Centuri bothered to use real world politics, theories and plans when making it's factions so we could identify with the tree hugging Gaians, the capitalist Corporation, or the bloodthirsty Spartans. I remember them! Notice I can't name a single faction from Beyond Earth. There is the Asian one, and the American one, and the Indian one, and the African one (who is obsessed with villages and their being built on trade!)
They oversimplified Aliens.
For such a massive part of the game, the aliens start off annoying (which is good) and then a single upgrade later, they cease to be an issue for more or less the entire game. I've played several games and unless everyone is going alien kill crazy (and I promise you, 70% of them will not have), the aliens wil cease to matter past turn 40. I'd honestly suggest they remove the anti-alien field, and force you to have to deal with them constantly, but make the AI better so they also leave you alone if you leave them alone. They also treat ALL humans the same, basically, so it doesn't matter if you're hugging or blowing them up, they'll basically aggro everyone, making it a Prisoner's Dilemma where the best move is to not engage the aliens collectively, and thus removing the largest part of early game fun. In Alpha Centuri, we are constantly learning more and more of the aliens, they surprised us more and more and are part of this massive setting. In Beyond Earth, they're boring green bugs from Starship Troopers without even the interesting brain bugs.
They streamlined the game, and it's somehow even less balanced and more complicated than 5
It takes a special kind of genious to make something simpler and it's still more complicated than the previous system, but they have fucking done it. All that rich history and over a hundred units is simplified to about 6, which updated 3 or 4 times over the game into slightly different units. It sounds fine in theory, but it makes a such little difference as long as you're on the same tier as the others. They streamlined health, now it's even worse while it does nothing. They made the Social Policies more streamlined, by making it so two of the trees are amazing and the other two are complete shit, so at least you don't really have to choose. They streamlined the economy, by simply removing most of your buildings and forcing it more or less on just trade (which is overpowered and then some). They streamlined the combat, and now without that variety, it's just boring to watch and look at. They streamlined the user interface, it's now hideous and hard to navigate despite being simpler and having less to keep track of.
It must be said; they made spies better, but they're also stupid powerful.
It's a massive step back
Almost every single problem I have mentioned doesn't exist in Civ 5. Which means they made a great game, learned their lessons from making it, and then decided to ignore it when making Beyond Earth. Beyond Earth is literally nothing but a combat game. Every other win condition is fucking terrible, and forces the game into a race of "Who can build the Mindflower first?", possibly the most anti-climatic thing in the world. The World Wonders are boring and uninteresting. The Diplomacy system is so stripped back and broken it's pointless to use, and the faction system is so badly set-up there is no point bothering to try a peace run because 2/3 people will hate you regardless and unless you drive just down that one path (Harmony is the best, we all know it), you'll get fucked over by people who specailised. Your faction, despite having more choice at creation, means nothing. The religion system? Gone. The City State system? All character (and there wasn't much) is removed, meaning there is EVEN LESS to do. The science system? The web is a good idea but it's a fucking mess to navigate and there is such a thing as too much choice (as well as the affinity mostly coming from there means you'll be researching affinity, not technology, which is the wrong way around to do it!). Building something means nothing in this game. The barbarians may not be much, but they kept you busy in the early game until you were big enough for the other Civs to take over. In this game, it's just so boring and slow for anything to happen, and yet it's too short for a good paced long game. It'll be long and boring and then someone will build a building and you'll lose because reasons. The appearance of the game tries to be sci-fi and just looks cheap and tacky and painful to look at, factions are completely interchangeable, the setting is ashamed and hides away in Wiki pages, and it's so painfully slow between turns I hope you brought a book. (I'm talking Rome 2 levels of waiting).
But...
It'll be good. Once they released both expansion packs, to fix the beginning, the aliens, the religion or equivalent, a late game choice like the Liberty, etc, FIX THE DIPLOMACY OH MY GOD, make the U.I. better, add choice, add character, add settings, add more than the same 20 quests, and generally make the game fun and good.
All they should have done was re-released Civ 5 Brave New World with the new start done better, the quest logs and updated pictures. They completely missed the new Civ 5 market, and they utterly disappointed the old Alpha Centuri market.