*contains spoilers up to episode 21 when I dropped it. I've seen beyond this one season.*
I was wondering why the ratings were so high as the previews looked like an isekai slice of life show meant for kids. That's exactly what you are getting and not much more. It's something you can turn on when you are wasted on a Saturday night and your mind can't form basic words, and it has its "cute" moments, but it definitely does not deserve an 8 with how childish, nonsensical and slow the plot is.
Let's start off with some of the good things before I start rambling with a long diatribe. There can (initially) be some good moments of familial bonding and emotional interaction as the MC comes to accept her new family. The constant buildup of suspicion and the ultimate reveal when one of her friends learns that she is playing an impostor, and justifying the act, is a novel concept and convincingly led well into. (the question of whether the body of the girl she took over still contains the original soul and is alive or not is sadly ignored thereafter) Other isekai anime usually gloss over such an obvious rabbit hole. Her chronic illness seemed like an interesting handicap to keep her from turning into the next davinci too soon with her grand knowledge of yet to be discovered technology. She also uses that knowledge to drive the plot along instead of it relegated to making bento boxes or being completely ignored altogether. The show thus stays pretty decent in the first handful of episodes as you get to learn about and experience these things for the first time.
But then the repetition starts kicking in, the intelligence of the characters become more and more questionable, and little things that were overlooked during the honeymoon phase start to grow irritating. It's hard to judge the simplistic nature of plotlines and interactions too harshly since this anime is ostensibly meant for kids, but I'm ultimately reviewing this for anyone beyond the single digit age group.
The MC is supposedly a very well read, intelligent young adult who died and had her soul transferred into a small child, but her mental capacity and mannerisms are frequently limited to that of said small child. This juxtaposes sharply against some of the thoughtful exchanges and critical thinking she delivers when recreating products, negotiating sale contracts, or arguing on equal terms with adults over political issues. As the show goes on, she becomes less and less capable and seemingly more and more clueless about the world around her, ignoring social decorum and blindsighted by the most obvious developments, while pouting frequently and prone to emotional outbursts. She basically devolves into a self-centered, screaming two year old toddler that can't understand anything and never learns anything or can see the bigger picture.
The other characters also seem to grow worse in personality. In the beginning, they at least had some "character" to them to individualize their interactions with the MC. But eventually they all turn into the same, smiling, copy paste member of the MC's harem, a harem of love, sunshine, and friendship. Conflicts are resolved too easily and with little consequence. There are no villains. It's as hei-wa as can be. Even darker or emotionally disturbing situations are swiftly cut short with rainbows and unicorns. It's a very child-like naive view of the world devoid of any realism. Yes the show is meant for children, but it doesn't seem to aspire beyond that, even in subtext.
And the mechanic where her chronic illness constantly leaves her debilitated is extremely overdone. Quite literally half the screentime is of her fainting or feverish in bed. It becomes burdensome very quickly in advancing the already slow plot. Her development of new ideas and inventions frequently hits artificially created snags that are very poorly conceived and juvenile. She tries to dry some stone tablets out in the forest but is too dumb to take them with her or cover them when it rains. The other kids jumping on said tablets and ruining them out of nowhere is also highly manufactured. And the dumbest by far is when she goes out to carve plaques out of wood to write on, but leaves them stacked next to the firewood in her house. Half her house is literally shelves and shelves of nothing but firewood, and she nonchalantly just places them among the many piles. Her mother burns them of course, and the MC literally dies from the shock. It's supposed to be a pivotal moment in the story when she learns about how her fever can immediately consume her if her spirit and resolve to live falters, but it's brought upon by something ridiculously stupid and the dramatic reaction being equally as stupid.
The slice of life stories get more and more ridiculous and contrived as the narrative progresses. Even as the MC goes on to do grander things and solves larger problems, the way she conducts herself and how they are resolved get dumber and dumber, as does the world building. Later in the show she randomly decides to join a church priesthood because she wants to read the books in their small library, knowing absolutely nothing about the religion of the church or the ramifications of being a member. The church she is a part of apparently has sex slaves, locks children up like puppy mills in dark basements, uses trickle down economics for food distribution, and somehow expects the people there to survive and become highly coveted and educated servants of nobility that fetch a high price, all while being a house of worship where not a single person is actually pious, while also harboring spoiled nobility that conflicts with the whole notion of asceticism. Two problem children in particular that become the MC's "retainers" are so bratty it's incredulous they were supposedly starving skin and bone just a few months prior with zero interaction with the outside world.
And ultimately the kicker that made me drop the show was when the plotline involving the MC's close friend, and his family's disapproval of his merchant apprenticeship, finally stopped dragging on and came to a line snapping conclusion. The premise was already terrible to begin with. This close friend comes from a family of craftsmen who make things. He wants to become a merchant, who sells things. In literally any culture imaginable, these two professions would have a symbiotic relationship. But for some unfathomable reason, his family objects to him becoming a merchant. No concrete reason is given. The disagreement comes to a head and the MC butts in to mediate an intervention. The poor and ill-bred parents, as smug and self-assured as can be, even though they can barely feed their own children or understand the simple concept of money for basic survival, cannot give a single credible reason for objecting to their son becoming a merchant, or even complete a coherent sentence for that matter. Yet somehow the case is resolved by the son apologizing, at his father's command, and everyone smiling and trotting merrily out the door in dance and song. This is somehow also made out to be a life lesson or "moral of the day" that the MC is taught, the moral being she should not interject and instead hear both sides out, even if one side is completely toothless and irredeemable. I don't know what they are trying to teach kids these days but it definitely isn't how to reason or make any sound judgment. In fact, we should praise the irrational, the nonsensical, and the ugly, as long as they scream the loudest and make the biggest scene, much like anime ratings and hype on the internet.