I love Canon Remus and all of his flaws. Enough of this "Casanova of Gryffindor Tower" BS, Remus is the cowardly lion of Gryffindor tower. He values bravery because it is something that he lacks and yet still strives to be. He has an ingrained sense of shame and self-loathing and an inferiority complex that stems from society's contempt and marginalization towards Lycanthropy, a condition he was cursed with from a very young age. He wasn't a leader, he was a follower. A blind follower who believed to his core that he was unworthy of love and respect because of what he was.

Which opens the door to what I believe to be Remus' greatest flaw: His unwavering, unquestioning devotion to Albus Dumbledore.

I think Remus saw Dumbledore as the perfect encapsulation of Good. He was everything that Remus desperately wanted to be, everything that society was determined to believe a werewolf could never be. And maybe, if Remus could earn (and cling to) Dumbledore's favor and make him proud, he would prove to the world and himself that he is Good, too, in spite of his lifelong curse.

Remus felt that he owed Dumbledore a debt he could never hope to repay for allowing this chronically ill little boy into his school when no werewolf before him had ever been given such an opportunity. So many of Remus' choices in canon stem directly from this imagined debt that he had dedicated his life to paying. Hell, he didn't even hold a grudge against Snape for OUTING HIM to the entire wizarding world simply because Dumbledore trusted him.

Remus trusted Dumbledore wholeheartedly. And Dumbledore personally saw to Harry's placement with the Dursleys. Why should Remus have considered, for even a moment, that Harry wasn't safe? Certainly far safer than he would have been with a monster in close proximity, as Remus believed himself to be. In his mind, staying away from Harry was what was best for Harry. Until Dumbledore needed a favor, that is.

It's reductive to suggest that Remus failed Harry (and by extension, James) for putting his trust in Dumbledore to do right by Harry. James and Sirius trusted Dumbledore, too. They all did. Stripping away all of the nuance and blaming the abuse Harry suffered on Remus is simply unfair. NO ONE helped Harry, not even those who were fully equipped to do so, and Remus was the farthest thing from being equipped to take that on, what with being an impoverished werewolf living in a society that reviles his very existence. The only person who could have saved Harry from the abuse was the very man that placed him in that home, the very man that Remus revered with blind conviction.