No nothing against the Japanese writers, it's just that the majority of the content is the same basic formula. It's the 'different' stuff that seems to catch on in the west.
That's arguable, you're considering the stuff that you deem acceptable in terms of watching anime, such as adult themed anime, which is fine, but a lot of the stuff popular in the west is the teen oriented shounen anime, such as dragonball Z in its time and more recently naruto, one piece or bleach. All of these reuse the exact same patterns(nobody 15years old becomes a hero, new evil guy appears and beat the hero/do something evilish, hero trains to get better powers, beat the evil guy, new evil guy appears etc). Char design and combat tend to be the strong points of the genre but they're anything but "different".
Also the harem stuff isn't that popular in japan either, it's not just over here. It's fairly small impact and is mostly made as a way to sell merchandise and uncensored DVD/Bluerays. Unless what you meant by harem was everything with cute girls in it, in which case I agree that's the large part of the anime market, but almost everything has cute girls in it because well, that's how TV/entertainment works.
However where I mostly disagree with you is the fact that FF does the "same basic formula" in their stories. It's exactly because they do NOT do this that they end up with absolutely fucking shit story. You can't look at the story of FF13(and the other games linked to it) and tell me that's basic. In fact it's quite the opposite, and by mashing together completely senseless elements for the sake of having them, the story becomes inconsistent and confusing, making the game shit.
In western game terms, this is Mass Effect 3 ending. Mass Effect 3 ending tried something different just for the sake of being different. It was absolute shit. If the game ended with a very basic "you save the world, gg", while a lot of people would have said it wasn't a good ending, they also wouldn't have said it was the most terrible ending of all things. The modern FF, and to an extent even older FF, always have tried to make shit cool by making them as alien and weird as possible. Sometimes it kinda works, most of the time it's just weird and people dislike it, and that includes in japan. They go with convoluted developement because that's what they think is a twist.
Regardless though, in no way a FF being written by US or european writers would automatically be better than modern FF stories. I mean it might not be worse cause that's not terribly hard, but it doesn't mean it'd be better, and they could easily have japanese writers make cool stories. The issue is more in the mindset they're in and what they think a FF story should be like(crazy unrealistic stuff at every corner so people FEEL THE FANTASY or whatever the fuck) than the fact they're trying to produce all the same shit. I guess they do follow that formula though, that everything has to be completely different, but that's hardly a "basic" formula.