It is the simplified form of music I don't understand - it doesn't go any further than my ears, I don't get the musical message.
Mariah started out her career at the end of the 80's singing ballads over pretty melodies. That stopped being in fashion by around the mid-nineties, where people preferred simpler, catchier songs over sweeping, orchestral songs.
Even in hip-hop, something despised by older folk, there has been at least a decades-long lament regarding the over-simplified lyrics and song structures. Nas, considered one of the top 4 or 5 rappers of all time, released a song titled "Hip Hop is Dead". And this was around 2008. This was to no avail, since the derisively-titled genre of "Mumble Rap" has now become popular, characterized by rappers singing lazily delivered nonsensical music.
Further more, Rock & Roll is completely dead. It has no presence in mainstream music. A shocking thought given how utterly dominant the genre was for most of the 20th century.
I guess young people, for whatever reason, just like simple tunes, and it's killing music. But I do like the song in the OP due to that infectious beat and Maria's delivery. Near the end, she does her famous "whistle register" to cap it all off.