Mario can't even talk though. He's pretty passive when it comes to development. When I read in Luvbi's article, there's hardly any mention of the Mario characters, no interaction. I don't know if the Wiki has incomplete information, so I can't verify myself (don't feel like sitting through potential hours of footage). Heck, it's stated in the article that she constantly put others down, so she doesn't come off as a pleasant character. Additionally, Luvbi appears to arrive too late in the story, in Chapter 7, to actually have any development with Mario. I have a feeling her relationship with Mario is overstated.
Her character arc revolves around hyping up for her sacrifice only for her to reincarnated inexplicably which, if you take the story seriously, should be a moment of inexcusably poor writing. Even if you care for the character, that should elicit a sense of betrayal by the story-tellers that manipulated your emotions for the result of status quo.
Either way I think any relationship Mario and Luvbi could've salvaged could've been done way better with Luigi or Tippi, one who is directly related to Mario while the other comes much earlier in the game.
And I would argue it would prove my point. Bowser's marrying Peach is all a subversion for the main plot. It's set up literally by one of the villains and revealed almost immediately. They want to set you up thinking it's a Mario story where something surprising happens, a wedding ceremony, but that's not a big part of the story at all. It disintegrates into another kind of love plot that doesn't involve these two all that much. I don't find it all that remarkable myself but I can't blame you since I'm spoiled myself and I also don't prioritize the plot all that well. I might have been impressed when I was 14 and was writing fanfic, but I'm 24 now and my idea of what's a good story has changed.