That sounds absolutely horrible. Why would I want to struggle and fail in an activity I engage in for fun? I've been a gamer for over 35 years, and I completely do not get the concept of games being fun because they are hard. I mean, sure, let somebody develop a 4X game for masochists, just please, don't let that game be Civ 7 - that would be the first Civ game I wouldn't buy.
That's very valid answer, and I know there is no way Civ series would become such "Souls - like" game due to the large amount of its fans who play it for that relaxing zen flow, which it generates very competently.
That being said, let me answer your 'why'. I suspect there are also many Civ players, like me, who are simply bored by the
lack of challenge, which kills their
motivation to play. For me the high difficulty in any game means adrenaline, emotions, the feeling of triumph and satisfaction. It makes all those mechanics and modifiers feel
meaningful, as in, you
need to exploit them cleverly to win - whereas low difficulty in all sorts of games makes me feel 'what's the point in accumulating all those bonuses, I can win anyway while not bothering with them'. It makes me feel more immersed in the game, as I need to pay more attention to it, sink in it more deeply and as I feel ups and downs. High difficulty makes for a better
story than a relaxing sandbox in which I can forget half of mechanics and still win comfortably. It makes for a better
adventure.
In the same time, Civ fails to make its approach to scalable high difficulty fun adventure, merely masochist and unfair. Deity slaps an absurd amount of AI bonuses on top of the same static game of exponential snowballing increase. That doesn't turn the game into a dramatic story of unexpected turns, where you can fall disastrously due to your hubris, or epically rise against odds. You just get extremely frustrating bottleneck of an early - to - mid game, where you have few few and very specific algorithms to hack it, and once you manage this hell you can cruise to the snowballing victory with the same boring certainty of the lower difficulty levels, just later. Thus, lower difficulty levels are too easy for my taste, while higher ones generate the most unpleasant, unimaginative kind of 'challenge'. Hence my dream of a 4X game which is challenging, gripping, dramatic fun adventure.
Paradox games can scratch that itch more easily, because they are chaotic simulations where you cannot predict everything. One of my fondest memories of EU4 is my Ottoman Empire having to suddenly deal with the simultaenous eruption of (late 18th century equivalent of) a world war and revolution. At one point half of my empire has fallen, and I had to desperately defend gates of Istanbul while bringing out every economic trick to avoid bankrupcy, and praying for Frech counteroffensive to take some German pressure away from Balkans. The war ended with miserable, hard - fought white peace (sort of like ww1), but God did it feel like epic history. Civ6 fails to recreate such moments because of its predictability, snowballing, combat system AI cannot grasp, purely bilateral diplomacy which cannot generate cascading wars of alliances, and complete lack of internal stability of empires.