There are many imbalances in the Game, but I consider them secondary behind Bugs and AI, mainly because they are nothing that Mods can't fix, but Bugs and AI not. So I'm not that bothered about them as much as others.
What really bothers me, and this is a hot take, is the fact that the majority of Players got a nice DLC Pass with plenty of Civs/Leaders, new Content and Game Modes, but I enjoy nothing of it. As some of you may have noticed, I'm not a huge fan of new Civs/Leaders, the Civs I care about and want to play as/against are already in the Game, and if I want a new Leader/Civ then the Workshop would already have what I want (The Only Civ from NFP I appreciate having is Vietnam). The other Content, like Districts, Natural and World Wonders and the Game Modes were very underwhelming for me. We could have had much more interesting and "realistic/historical" things than the ones we got. And even on their own, they have plenty of Issues. The Game didn't need those "Colorful, but Shallow" things, but some love to existing Mechanics that need some improvements, Fixes or rework in some cases, and also Fixes to the many, many annoying Bugs that are still in the Game since its release, like the Unit Pathfinding Issue, which alone speaks a lot about the Game's QA. No, what I got from NFP are Things that I don't enjoy, and Many Bugs and constant Game Crashes on top of that.
The biggest Bug pre-NFP was the Crashes that were caused when you played on some modded larger Maps. So, something annoying for many Players, but not something that was disrupting you from enjoying and playing the Game on its own. But NFP's Introduced Bugs can't be ignored, they don't just stop me from enjoying the Game, they're also Game breaking:
- Constant Crashes for no obvious reason (even without Mods), which never, or only in rare occasions happened pre NFP.
- Graphical Glitches that even if they don't affect Gameplay, they still are immersion breaking and disrupt the enjoyment from the Game's Visuals.
- Game getting trapped in an infinite loop when hitting next turn, which happens at least a couple of Times in a single Game.
- The Asset Limit Bug. There is no reason for this to be there, bc pre NFP you could enable all asset Mods in the Workshop and still play the Game just fine. For the Larger Maps Bug we have at least the Disasters and Climate Change Mechanics as possible causes for the Issue, but the Asset Limit Bug has no explanation for being there, bc none of the Game Modes were major enough to explain some core restrictions. And quite frankly, I despise NFP for this whole reason, bc it didn't even introduce any major Mechanics or reworked existing Ones that I could at least have as a consolidation, I could do without them (or NFP as a whole) if it means no Asset Limit Bug anymore. You can say that this is outside of the Game's Sphere and that it doesn't affect the Game on its own and that's all what matters, but I would disagree, bc A) although I like Vanilla Civ6, I'm only playing the Game because of Mods, and I don't want to invest in a Game that doesn't consider/support Mods, B) It might be the case that Civ6 may thrive without Mods, but only as long as it's supported by Firaxis. The Longevity of the Game after the end of its Dev cycle is mainly in the Hands of Modders/Mods, but if you put those kind of restrictions on Modders, then don't expect a great modding Scene, C) it might as well be the reason of all the random Crashes, even without any Mods.
- Game Mods Bugs should also be listed here, and not ignored bc they are optional (very weak excuse IMO). I have paid for them, so I want them to be playable, but AI not improving resources, the tremendous Monopoly Tourism Bonuses, AI suffering from Dramatic Ages, AI not using the Game Mods in an acceptable manner (I'm not expecting smart/effective usage)...etc. all of that prevents me from even playing with those Modes, how can I then give them a chance? I dislike most of the them, but I still want to give them a chance, but I know I will just exploit them, while AI either doesn't or suffer from them. So, what's the Point of them? I'm not the type of player who gets happy for getting a Win handed in the form of a silver platter of Icing/Toppings (that don't even taste good).
- Various other Bugs that you can find in plenty of Threads here on CFC in much more details.
Those are a lot of Bugs that aren't just annoying, but also prevent me from enjoying the Game, or more often than not, they even prevent me even from playing the Game. I honestly can't believe how unstable the Game has become since the introduction of NFP. And like P0kiehl pointed out, the Quality of the Game has also declined a lot since then. What once was a nearly complete and stable Game, is now a way-further-from-complete Game, that got/is getting some new "shiny" but hollow Features/Content with NFP/LP, instead of a Final Polish and Bug Fixing that could have left this Game in a state that would have helped a lot in its Longevity. It's really a shame that after the Devs poured so much work and heart into the Game, and made it the Game that we all love and enjoy, but now leave it in this only-half-enjoyable, incomplete and unstable state.
Don't get me wrong, I'm not trying to talk down on the Devs, I'm really grateful for all the work they have done, and appreciate their Investments put in this Game. But truth be told, I disagree with a lot of their Decisions made, pre-NFP as well, but in NFP in particular. I'm also stunned that the main Designers were the Opinion that the Game was complete even before NFP, and more so now. The more I read and watch them talking about the Game, the more I have the Feeling that they don't pay Attention to details and the State of the Game as much as we do. Too bad. I get it, after spending several Years on a Game, there always comes the Point where you just want to finish it and head next to the next thing, to something completely new. But why NFP then? coud just have made a last Game Patch and then focused completely on Civ7, or Spin-Off. And also, wouldn't you also want to finish it in a good and stable state, after all the efforts put into it?
Yes, yes... 2K, Take2, Higher-Ups, limited Resources and all that, but Firaxis are still the ones who decide what to do with those Resources, at least the specific Design decisions to make for the Game. And I'm not happy with the Design decisions made since NFP. They didn't bring any Value to the Game for me, except annoying Bugs.