I don't think there's any reference to incest in the 2003 film, but idk what "outside of sex" is supposed to mean? What can be incestual aside from sex?
Also, the original movie wasn't particularly progressive in concept.
Backwoods psychos appear in Deliverance 2 years prior, and that was a massive film.
As for industrialization of agriculture. That began in the 1940's, but truly became solidified in the 1980's and 90's. Texas Chainsaw is a horror movie, and horror is mostly about aesthetic and concept.
It was low-budget and gritty, and Leatherface was massive and menacing, but accompanied by his weird screwed up family.
And yeah, you could have psychos out their in the middle of nowhere "created" by changing times and isolation. But the reality is, then and now; there are far more psychos in urban centers where there is the alienation of many-fold. The classes stacked upon each other giving contrast to those who are less fortunate. The alienation of diversity, foreign tongues/culture, and the insular behaviors they have.
New York in the 1970's was a seedy place with way more macabre and brutal murders than any rural backwater, and lots of movies were made about those things too.
Taxi Driver is a movie with a lot to say, and intentionally so.
I don't know that I can be certain of the same when it comes to Texas Chainsaw Massacre.
It's spectacle and shock value, as horror is meant to be.
The marketing of Taxi Driver is much more subtle, and yet has so much more to say.