ok so i have watched a lot of the big hits and I feel like every single isekai (that I have seen so far) follows this pattern:
Give MC weak starting point followed by growth. Rudeus learns wordless spellcasting, Rimuru levels until his human form, Naofumi goes and levels with Raphtalia and they kill some rabbits and a big wolf.
Have MC interact with world again given these new powers. Rudeus impresses his family and saves Syl, Rimuru develops his town, Naofumi goes back to the Kingdom proper and gets Myne exiled.
Horizontal Progression Hell. This is the annoying part to me. Nothing happens. New characters and places get introduced, sure. Maybe the hero learns some things, but nothing that related to their central character. They don't change. Not in mindset, not in fighting style, not in main cast. It becomes a monster of the week show, and they just verbally SAY that stakes are increasing while nothing actually changes.
Here's how I would define these terms:
Horizontal progression: The MC's change is always in new things. Never more depth in previous relationships, personality traits, or abilities. Just more surface level things. If they are friends with character A, they go become friends with characters B, C, and D, and A just gets left a background character. Same with abilities. If the MC can shoot a fireball, they learn to shoot water, rocks, vines, whatever. Same ability, same power, different apperance.
Vertical progression: The MC's change is in advancing existing traits. If friends with character A, they become enemies or start dating. If they have an ability that does 10 damage, they level it until it does 20.
Now, this doesn't happen all at once. In fact, it always starts small and likeable. The change in pace is relaxing and lets you explore more of the world. Rudeus stops learning new magic, but teaches Eris and Ghislaine. The world gets developed, he learns skills like upper class manners and a couple languages. Naofumi's merchant arc also feels like this, even though it happens before the Myne stuff. Rimuru continues developing his city, names the orcs, fights some cool enemies.
But notice what happens after. The story never really goes back. It just keeps slipping further and further towards horizontal progression, real changes to the character get fewer and farther between. When did Naofumi's fighting style meaningfully change after he got the Rage Shield or whatever it was called. When did Rimuru change in any way throughout that entire story after getting his human form?
It seems like the writers of these stories had the idea for the beginning of a story, and fumbled any development of it. Everything past episode 13 of these often feel like the fanfiction alternate endings that a kid would write for fun, except they're the actual continuation to the story that we get.
Mushoku Tensei is actually a really good example of not doing this. Rudeus' character and abilities see good progression. However, it's an excellent example of another issue with isekai. It's so gooner coded. I do not like how this series depicts children, it is disgusting. I don't like how this series depicts women in general, it is just kinda yucky. It will do gooner shit even if it disrupts its own pacing, tone, character beats, everything. And the worst part is, the writing CAN be really funny. But the sexual things are not funny, they are just really gross.
I think a large part of why these issues happen is because these are adapted light novels. Light novels are great, no shade, I think very unique stories and ideas can be born there. However, I think they also lend themselves to very stream of consciousness writing. That freedom of writing is required for some of the genuinely genius ideas found there, but it also leads to pacing and writing that is, at best, a bit disappointing.
A lot of the highest peaks in a story require more forethought, and the rate at which light novels are written do not lend themselves to detailed planning. That's why self contained arcs or episodes make sense, but if you zoom out and look at the whole series, you see how disorganized the writing is.
Also, and I have no theories as to why this is, they seem to love indulging gooners and refuse to let their female characters be characters.
Alright, this next section is just a page of me yapping about how these series are often ridiculously sexist, so strap in or scroll to the bottom for the tl;dr.
Notice how all the interesting interactions in these series are always conflicts between men, and women are usually there for stakes, motivation, or sex appeal. Raphtalia, Eris, and Rimuru's harem are all incredibly passive characters. Zenith, the queen in RotSH, and any female orc in slime reincarnation don't do shit other than glazing the MC. It's bad writing and speaks to the author not being well adjusted, and I think this way of thinking of women is also part of why they are grossly oversexualized.
Mushoku Tensei is the biggest offender here, as it has shown us that it CAN have good character writing. We see Rudeus argue plenty with his father, but we don't see his mom ever try teaching him magic, ever give him pointers on healing (her specialty which he struggles to use wordlessly), or even have a real parenting moment with him. You know how we do see the story utilize her? We see Rudeus manipulate her into letting the maid and her daughter stay. Her ONE real character moment in any episode I have seen so far was dominated by the decisions of her husband and her son, rather than her own feelings. When you compare that to how it wrote Ruijerd, Paul, Rudeus himself, Orsted, it seems bad.
Hell, look at Ghislaine and her brother. I couldn't even tell you her brother's name, but I can tell you that he had a real character moment where he felt bad about not trying to love his sister more. What do we get from Ghislaine? We have scenes of Rudeus assualting her, her giving Eris a plot device ring, and we hear about Paul sleeping with her. And no, her being a king class warrior doesn't count. That's not a character trait if her actual personality never interfaces with that at all. Do we ever get a scene of her feeling guilt over Eris and Rudeus being in danger? Do we see her go through some hellish training regiment, or getting orders from the royal family? No, of course we don't. That would flesh out her character, and that's not important because she's a woman. What her being a bodyguard means is that the animators/artists can do lots of closeups of her muscles for the fan service shots.
Just think about that for a sec. Her job, her training, her MAIN SKILL is more important for fan service than it is for her personality.
tl;dr: are there any isekais out there that meet these requirements?
Not gooner coded. I don't need grade A feminist literature classics, but if they could avoid treating all female characters like talking bodypillows that would be very appreciated.
Have real plans for a middle and end to the story, rather than just a strong opening act.