Look incredibly dated for a 1976 movie.
Other than the afros, it looks and feel like a 60s movie.
I thought so too.
It was shot in 1975, but looks like it came from the era of "When Dinosaurs Ruled the Earth," which was shot in 1969, or earlier, e.g. "The Lost Continent," which was filmed in 1967. The Pellucidar sets look like something out of the original Star Trek series, which ran from 1966-1969; maybe a little better than that, but not much.