Pretty much what everyone else said, it's a bit cruel to the readers to make Itsuki win after showing sympathetic romantic interactions with every other quint.
I don't hate her. And I know that in fairness, the romantic interactions with the other girls were all one-sided, Fuu-kun just grew more fond of each girl without truly falling for any of them. So it's not like the author is really contradicting himself in any way with this development. But yeah. It feels like this arc is when Itsuki realizes she needs to stop trying to be her mother, and allow herself to fight with her sisters over Fuu-kun.
Sometimes stealthy character development accompanied by complex foreshadowing just alienates readers. Itsuki needs a huge and meaningful arc if the author wants readers to accept her as best for him... yet she already has this longer arc and a unique status as "the only one who doesn't love Fuu-kun" "the only one who hasn't appeared to kiss Fuu-kun", in a way that makes it easy to feel like the author has locked himself in by designating her as the "special one".
So yeah, tl;dr I'm okay with Itsuki as long as Negi doesn't just let Fuu-kun fall into her lap after the other quints actually had to work themselves to the bone emotionally in order to close the distance. But right now at least, she's in fifth place for me.