That doesn't have to do with technique necessarily... classical singing is generally more strenuous than pop singing (I say generally because Mariah's music is an exception.) Classical singing is an entirely different discipline: you can fuck up your voice just by singing the wrong roles.

My point is that "classical technique" is glorified as being the "correct way to sing"

The thing about classical singing is that it's just an aesthetic. It's an aesthetic that promotes good technique, since classical training generally will give you good technique because of the emphasis on support and placement. However, as with all aesthetics, it can be done (to an extent) without good technique, and consequently there are plenty of opera singers with relatively bad technique and short careers (and, conversely, plenty of pop singers with good technique.)

celebrity "vocal coaches" rebrand this technique and use it as a marketing gimmick

The technical basis of singing is the same regardless of genre. You can definitely learn to support and place your voice correctly and eliminate tensions without ever touching classical training. It's not how you get there that matters. But good classical training will get you there.