The cultural impact is to prove that setting a new bar for mind-blowing gorgeous CGI was still possible a decade after Babylon 5. The Way of Water repeated that incredible feat.
I didn't watch that Fire And Ash yet; so don't know whether it further ruins every single other modern movie further or just keeps them disappointing by reinforcing standards which seemingly no one else is willing to consider.

James Cameron proved that there is a massive market for movies without witty punchlines and convoluted plots which require one to have the booklet (or nowadays phone) at hand to read along like when going to the opera.
He took the most overused classic western plot and made it work great on the big screen for a heterogenous global audience. He didn't need any well-established franchise to back his adaptation of "White men invade land of natives; all hope is lost. But then one of the whites turns out to be the savior and helps the natives to repel the invasion."
It was refreshing to watch a movie that let me pick a side without coming up with some forced gotcha-everything-is-morally-gray bullshit. That shit even infested the comic adaptations by now.

The plot couldn't be more bland. The characters couldn't be more forgettable. The movies still are masterpieces regardless. Yes, I cringed at some points. But overall, they were a great experience. And yes, I also like Western.

Btw, Papyrus is a fitting choice for the title font.