The “correct me if I’m wrong” line was supposed to be a joke, I didn’t think you believed aliens or Atlanteans created the Sphinx.
With regard to the age of the Sphinx, I don’t think anyone knows the exact year, but the archeological evidence (or lack thereof) provides a clue. The picture you included may appear to be water related but may not actually be erosion. Afterall, early astronomers thought that Mars had canals based on what they saw in telescopes—most of what they thought were canals were wind erosion. I’m not aware of any evidence that shows man in Egypt as organized enough to build such a structure more than about 5,000-6,000 years ago. Do we have any real evidence of an older culture?
There are no archeological remains such as 14000 year old cities anywhere and there is other evidence such as the genetic diversity of dogs which goes back about 12000 or so years which was around the time scientists speculate that humans began the less transient farming lifestyle which eventually led to the rise of cities and cultures.
I think Jehrico is one of the oldest cities in the world with evidence of a wall dating back @8,000 years.
That timeline of gradual development is consistent with what we know of human development which would put the Sphinx into the 4000-5000 year range.
I wouldn’t write off the possibility of an older proto-culture, but I would want to see credible evidence first.