I would rather think of major and minor as “light” vs. “dark” (respectively) instead of “happy” vs. “sad,” which are subjective emotions no matter how "indoctrinated" we are. Although the major=happy and minor=sad are compositional tropes cultivated throughout musical history, the singular dimension of mode, major or minor, does not itself determine a piece of music's "happiness" vs. "sadness" effect.
The saddest melody of all time, to me, is in the MAJOR mode and only outlines the MAJOR triad throughout the tune. It is called Taps and is traditionally played by a solo bugle at a funeral. The social context of this piece of music surrounds death, is performed at a slow tempo, and by a lonely solo brass instrument, all of which contribute as to why this is such a sad melody to me. The example I present here is from John F. Kennedy's funeral in 1963. This particular rendition of Taps is infamous because the bugler, Keith Clark, missed a high note. The mistake was misconstrued by the media as an emotional moment by Clark, a musical realization of "choking up" underscoring the deep sadness felt by the country at that very moment. It was just a technical flaw, however, due to the cold weather and Clark's physical placement near the firing rifle party which deadened his ears.
There are many musical factors and contexts that Westerners are “indoctrinated” to during their childhood and adolescence that contribute to feelings of happiness and sadness, not just whether the mode is major or minor. As observed above, tempo, instrumentation, and social context, mark this major mode tune as one of the saddest.
You can read more about Keith Clark and this moment in history at "A Bugle Call Remembered: Taps at the Funeral of John F. Kennedy" by Jari Villanueva.
Can you think of any examples of an upbeat, "happy" tune in the minor mode? How about Hava Nagila? Again, social context, tempo, and instrumentation play an important role as to why this sounds 'happy."