Citizen Kane's soundtrack is NOT mediocre.
I don't get 1940's and 1950's soundtracks besides Miklós Rózsa's (who was a true genius).
Anyway, from the videos you posted here I noticed that our music tastes are surely different. I noticed that I don't like mid 20th century music, overall, I like Classical Music or 1980's music.
Another problem of these old soundtracks is the poor sound quality.