I mostly play other strategy games, have a total of a couple 1000 hours invested into varying civ games, paradox titles and many other strategy games so I figured I'd give my perspective on the game. So nearing close to 600ish hour including offline time at the time of writing this review I can say that the game is worth it (Kinda).
The basic guideline is If you have another 4x game that you main you might want to get humankind at a discount (at the time of writing basegame is like 5$) and never regret it. If you are a veteran that got tired of your usual loop then something like 20-30 is a good value for your worth too and you're likely to spend around a dozen of playthrough which is around 50 hours in or so.
Now onto the review itself:
The Good
Combat - is by far the best aspect of the game. It blows any civ game out of the water easily and contends with all the fantasy strategy games in the highest leagues. Wouldn't say it beats HOI3-4's system but that's not its focus. Going back to any other game feels like a direct downgrade compared to the impact altitude and features can have. Only caveats would be the poor balance some units have (which mods try to fix) and the lategame never got fully developed due to the studio moving on. Water combat has a decent baseline but like many other titles around it just falls short to being a stat vs stat issue mainly won by the player that strikes first.
Economy - Again, one of the better implementations I've seen around. The fact that the resources (which are basically passive boons with extreme impact) travel around the map and can be targeted either during war or plain raiding is amazing. Securing the transportation of all the luxury or strategic goods going from your new world colonies to the capital actually has an impact. If you get raided on your critical sea node you can say goodbye to all the production and public opinion back in the capital which might threaten riots, collapse and inability to regenerate your strategic resource reliant units. Very simple and yet a very effective implementation of the system only falling short to Victoria series that entirely market themselves around economy
Victory conditions - Slightly controversial and definitely not everyone's cup of tea. But if you like building solid, well rounded and generally strong empires then you'll love its approach. Rather than have an arbitrary victory condition you are pivoted to just be the MVP of the game. Either someone that made the largest impact by fighting earning military points around instead of sitting back playing simcity or rewarded for rushing to gobble the new world as an expansionist reward. Anything you do will tie in with some other adjacent way of earning more rewards which will eventually lead you to having a well rounded empire that will win regardless whether someone 'ended the game' by hard focusing on a singular aspect.
Industry/Citybuilding - One of the prettier depictions to say the least. Most of it as to be expected, expanding your city to produce more things faster while balancing the expansion with happiness. The most interesting aspect of it however would be the strategical implementation of your decisions. Every tile you take will matter tactically in the case you get sieged. Making a city on a cliff will be a nightmare to take for the enemies moreso than any other game. Focusing your industry on a more open fertile land will make it more vulnerable and more profitable. Do you want to build around the cluster of luxuries to ensure their safety or make a stronghold that'd need a dozen turns to take. Small decisions, large impacts
Net connection - Honestly one of the more stable iterations I've seen. It was shit at release with constant reconnects, but lately the worst you might get a desync and it won't matter for a few 100 turns until someone can't move units which gets fixed by a reload and lasts another 100ish turns. Certainly beats the lobby simulators other competitors have
The Average
Diplomacy - Kind of ok. It matters more than most games but doesn't do too much. It's at least more interactive than most implementations. You can actually get resources for being a 'good guy' and then leverage it later on in the game but they are mostly tied to securing your casus beli. You can't punish the wrongdoers properly with diplomacy only, other Amplitude games like Endless Legend or Space did a slightly better job of it. Still, you can always use it in the early game to formally declare that you're angry at the forward settle and they better give you the land or else (and else gets mechanically guaranteed to start in your favor)
Spying - Not great, not terrible. It has some good applications by being able to cause revolts, weaken entire armies, trace movements but it's all super basic. To get anything out of it you have to pivot super hard and the payout is maybe ok. It also gets somewhat tedious to micromanage spies as units on the ground the longer the game goes on. If optimally used you can devastate enemies but still, I just dip into it for fun every 10th game or so. Rather just build more industry instead
Religion/culture - They're just stat sticks. I assume there was a plan to rework and fix how it works down the line but I doubt it will ever come to fruition. As it is it is kind of ok, basically used to fuel your diplomacy and military aspirations. Very ignoreable part of the game that advertised to be 'an iteration of random civilizations with odd cultures'.
The Bad
Ai - It's shit as every other game's. It may seem smart a few times but it needs economical buffs to stay afloat, has rudimentary flowchart for combat, generally predictable opinion modifiers. I wouldn't say it's particularly worse than any other I've encountered, just a generally bad 4x game Ai.
Bugs - Contrary to what you might have seen in the old reviews, a lot has been fixed by now. Game ending bugs happen maybe once in 50 games in my experience. Some minor annoying ones you can make workarounds for or just reload a turn. For the most part minor inconvenience.
Pollution mechanic - Turn it off. Turn it off and forget that it exists. Half baked placeholder since the beta. Likely was supposed to get reworked down the line like culture and religion to slow down growth in industrial era but as it stands it just makes the game painful to play.