I'm probably the biggest advocate for more story in Mario, character development within the game, and, dare I say, a slightly "darker" Mario... NOT emo Mario, but darker Mario... e.g. Mario in Subspace Emissary, Mario in Strikers Charged, but Weegee...
...you've gone off the deep end.
Even with how I feel about "childish" stuff in Mario games, I was not embarrassed by the Lumas at all. They're there.... aaaand they're there, what can you say? Piantas are basically dumber than Lumas.
On another note, I still don't understand why people, almost 2 years after the game's release, are still complaining about Rosalina's "bedtime" story....you know... the one that was (and still is) completely optional. I remember everyone saying "I will CmPLETLEY AVOID THIS ON THE GROUNDS THAT MARIO SHULD HAVE NO STORY OR THAT IT IS ST00PID" but then you will still hear complaints about how childish it was.