Arguably the most obnoxious thing about being a Fates and Nohr story defender is actually hearing people act like love as a force should be exclusively pure or redemptive. I mean love as a more complicated force; portray it as flawed and complex as any other human impulse, love as prejudice, love as possessive stasis, love as addiction, love as blindness, etc.
Many don't realize the Nohrsibs love their father and just want him back even knowing his horrible elements and how he wanted to kill them for fucking up even a little, and it's disturbingly realistic if you know people who went through similar abuse. And when people do that and don't leave an abuser they just go "that's not realistic" even when it is, because people just don't leave abusive families like that. Corrin in Conquest stayed because they didn't want to turn their sword against the world even if it damned him doing so, and people act like he's made a bad choice when many aren't even self-aware enough to realize in Corrin's shoes they'd do the same thing.
Love can be destructive, it can be selfish, it can be nostalgic and blinding.
Hell, love being tragic and doomed is a plot point present in the very first game in the series. The reason why Medeus' dominance of the Archanean continent got so far is partly because of Camus and Nyna being involved with each other, the former not following his heart resulting in him help conquer so many places and kill so many people. And unrequited love is what kickstarted FE3's plot, with Hardin succumbing to the darksphere because of his jealousy.
Love, along with fear, is what causes the Nohr siblings to be servile and deferential to Garon. It's not a simple matter of morals, it's a messy web of psychology. For Xander, Camilla and Leo, love is itself intertwined with violence because they the things their mothers and lost siblings were doing in the name of gaining favor from their father. They saw that as trying to gain love. They aren't able to compute what love for their sibling, Corrin, really is in contrast to their love for their father.
And then mix that with their status as royalty? You got a messy, entertaining family, who need to be exposed to some harsh truths to be able to free themselves.