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Second, I think it's safe to say that, in general, people tend to dislike change, especially when it comes to something they're comfortable with. If you disagree with this, you should probably stop reading here. But you may want to peruse relevant literature on this topic (such as
this).
With that, I think we can start with an illustrative example of the
Heroes of Might and Magic series.
Heroes of Might and Magic 3 might be one of the best turn-based strategy games of all time. Compared to its predecessors, it's simply bigger and better. By the time all the official expansion packs had been released, it's practically massive. So what could the developers do for the next iteration of the series? An even bigger game - more factions, more buildings, more creatures, more artifacts? It would really start to get unwieldy. There was not a whole lot more room to grow in those simple directions, not for a brand new entry to the series. So what did they do? They decided to streamline major parts of the game and add interesting, meaningful decisions at each stage. And lots of players hated the changes. Lots of them had good experiences with the series that culminated in HoMM3. They had certain ideas of what the series was about, and the changes, while not really deviating from the flavour of the series much, didn't conform to those ideas. They just wanted more of what HoMM3 offered, although how a new viable game could improve on that entry substantially was a difficult question. So HoMM4 is, by and large, considered a failure.*
*Of course, the thing that truly spelled doom for it was 3DO's financial troubles. But after the success of HoMM3, HoMM4 was definitely not close to being as successful. Sounds familiar?
HoMM4 was, in some ways, a victim of HoMM3's success. Its predecessor was so iconic that the many people who loved HoMM3 expected a sequel that was could satisfy their wants in the same ways. They rejected streamlining, for example, because it reduced the variety of creatures you could recruit in one town since you had to choose between Building A and Building B. A design decision that introduced meaningful decision-making and allowed new features to shine more (fielding heroes on the battlefield) was disliked because players saw it purely as a reduction, a downgrade.
And I contend that the Civilization series is going down this route.
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