I don’t even think Jerry likes slice of life. He just writes it because it’s simple enough for his smooth-brain(cause he can’t write anything interesting or complex).
I feel like, beyond that, it's more of a distaste for conflict driven narratives. After all, her way to 'fix' Harry Potter is to remove the central conflict. There is nothing threatening Harry, Hogwarts, or the wizarding world as a whole any longer. We can assume there's interpersonal conflict at school to make up for this, but Lily's other works show she's just as bad at executing even stuff like that. She has one idea for a conflict, and it's Character A (G, Aliana, whoever the fuck is her self-insert this time, etc.) does something bad like rape someone in their sleep or shock an old woman with magical lightning powers and Character B (Their helpless and co-dependent satellite) comforts them and tells them that those awful things were actually okay. The thing with conflict is it not only helps you build a character by writing how they react to conflict, it also helps you develop that character by writing how that conflict changes them. The evil dark lord destroys the protags village. Are they a brave character who decides their reign of terror needs to end, and justice be served? Or perhaps they're more pragmatic and focused more on surviving that reign of terror by living on the run than they are with bringing an end to it. Do they find self-fulfillment along their journey or do the woes along the way break them, turning someone once optimistic into someone bitter?
Lily's conflicts are often lacking in these as her characters are almost never changed by conflict of any kind. G does something bad, Lily forgives her and no lesson was learned because G keeps doing the same shit. Aliana is never emotionally or physically challenged by anything in TSR, so the villains pose no threat of any kind to her and no one ever forces her to question her motives, her ideals because other characters come in instantly to remind her that she is perfectly justified in killing a bunch of random rich people she assumed were war profiteers because she lost her mom a long time ago, okay? She's like thirty, she's basically still a kid! She keeps writing these really static characters who hinder the story they've been grafted onto. They become a stone wall no storytelling potential can get past because Lily refuses to do anything interesting with them. She won't challenge them in any meaningful way, just in this really sad kind of way where their flaws and conflicts aren't really conflicts. They're minor bumps in the road that Lily uses to trick her audience of sheep into believing things are 'going' somewhere or characters are 'growing closer.'
I can't help but feel this is due to her writing method being very much impromptu and by-the-seat-of-her-pants where nothing is ever really planned out and things happen as she finds inspiration for them. It turns all her projects into a clusterfuck of ideas that go nowhere and resolutions that feel unearned because she didn't know how to get the story to that point. The most recent TSR writing she'd done was like...a flash-forward to the future where Aliana is now dictator for life and adopted some child with Rey. How did we get here? I don't know. I'm not convinced Lily does, either, but she wanted to write about this so here we are. This is why I've felt she tends to get burned out on writing. She can't pace herself. She can't help but get ahead of herself and tell everyone what's going to happen next only to never write about that and skip to some unrelated new thing because she thought it would be cute if G was obsessed with Lily's hair and braiding it for a chapter because someone on her Discord convinced her it would be cute. This is probably the real reason she likes to write slice-of-life fluff, she's at much more liberty to bounce around between 'cute' and 'wholesome af' scenarios because those are just snippets in the life of her characters that don't really need to happen in any particular order.
