I've been seeing dislikes about these two new characters. In my opinion or much less a theory: Kagami and Luka are good for Mari and Adrien.
Because if Kagami and Luka come. They should be the ones to push Adrienette together. Kagami attracts Adrien while Luka to Marinette, no?
Like Kagami could actually talk to Adrien about problems he hasn't talk to LB or the others (without saying he's Chat Noir) while Luka helps Mari realize that not everyone even Adrien is perfect. He could at least give Mari new perspective on Adrien, rather than seeing him as the son his father sculpted him to be.
All I'm saying is that I want to see Luka and Kagami help Adrien and Marinette out. Also see the screenshot for the Riposte episode? Where LB is holding Adrien, we already have bets that Riposte is Kagami due to the obvious character hints.