Interesting. I can attest to analogue IMAX having great sound, however, if you watched an analogue film projection of a current film in the last 20 to 30 years, the audio was most likely digital anyways and I believe that is also true for IMAX, since the film itself does not even have audio on it. I suppose, a good audio master and especially a good audio system do a lot of heavy lifting.
And yea, hfr is meh. The effect it has on film is very underwhelming. The only film I have seen where it worked was Avatar. In Avatar 2 it works well in the scenes it’s in, however, the transition between the hfr and normal parts is extremely jarring and takes you out of the movie. The film you saw in hfr was probably one of the hobbit films, since it was a big marketing thing for them.