Well, as I said here, whether or not a game is forgiving or not has little to do with consistency that I brought up.
All and all, I think this makes the difficulty widely inconsistent more than it needs to be, and as a result it's very hard for me to tell whether it was a game where I actually played better or I was just being carried by my spawn. This isn't unique to this game, but with stuff like Harvest Goddess/Defender of the Faith/Crusade providing a huge early advantage to you (or a huge disadvantage against you), it makes it much harder for a player to get proper feedback.
You could make Civ 6 have its AI leaders start out with 4 cities. You could also have the game uninstall itself if the player didn't click the right corner once every 2 minutes. These things would make a game objectively harder and less forgiving, but it wouldn't solve a thing. It's not just about the quantity of difficulty, but also the quality.
It's important for a game to deliver proper feedback to how the player plays a game, at least for those of us who try to improve their gameplay. In Civ 4, it was hard, and it was also clear if your skills were not up to par but there was still a lot of flexibility in what to do. It's very hard to fluke out a win on high levels not just because it was hard, but you actually had to understand the game mechanics. But once you mastered the game mechanics, you had enormous leeway to pursue many options and make them all seem viable in strength. This is why I never even saw a need to play above the mid-levels in the game, despite the fact it would be "easier".
In Civ 6, I really don't know if I picked a good strategy or because the AI just threw the game. Why is it that sometimes the AI walls itself on turn 30, but sometimes not on turn 140? There's no reason for that. I built 30 war carts and won on Deity. Does that mean I'm better than someone that only plays on King? Actually, I have no idea. This is not true at all in previous games.
As a result, I may "win" in multiple games but I have no way of improving. And at a certain point, I stop caring and just treat it like a sandbox, which is fine, but not everyone can handle that.
There have been many, many complaints about how the game isn't fun past the first 2 eras even though that's always a problem-- it's because the bulk of optimal play is concentrated there. Optimizing a game that you've already won is so you can win even harder, well to me, incredibly dull.
Point is, Civ 6 is easier yet more shallower in its challenge. It's like a puzzle with only 1 answer while the rest is merely an illusion of choice. It doesn't reward the player for experimenting or trying something else simply because its victory mechanics cannot comprehend it. It's already the game with the biggest AI bonuses, but they just don't work for good reason.
tl;dr Challenge /=/ Maschoism. Well, at least to me
tt;dr 2: This is also why I liked loyalty in Rise and Fall. It doesn't make conquest impossible. But it makes it require at least some thought. And suddenly it got much better.