The isekai subgenre is one of the most popular, or perhaps most notorious, in all of anime in the 21st century. It's based on the idea of a protagonist finding themselves in another world with new people, new rules and new realms to explore, and while examples of this date back for many years, this unofficial genre exploded in popularity within the last 15 years.
In past decades, stories such as The Wizard of Oz and The Chronicles of Narnia were the exception, featuring characters who were displaced into another world, but now it's the norm, and not all anime fans are happy about that. Anime has many genres of storytelling to offer, and according to some fans, isekai has worn out its welcome. In fact, many say it's downright trash.
Why Anime Fans Deride Isekai As Trash
Aside from viewer scores on sites such as MyAnimeList and IMDb, there is no conclusive way to say whether the isekai subgenre is truly bad or not, or whether a particular isekai anime series is definitely "trash." It's a subjective take, but if enough anime viewers are all saying the same thing, then a curious fan would want to know why such a consensus exists and decide for themselves whether it has merit. The anime community has strong opinions on a wide variety of topics, from who the Best Girl of a series is or what should be in the new shonen "big three," and few topics appear more contentious than isekai.
Isekai is not a formal literary genre in the same vein as fantasy, mystery or romance -- it's an unofficial subgenre of fantasy and sci-fi, most often the former. Isekai anime titles tend to have similar basic conventions as one another, including the protagonist ending up in a new world by some means beyond their control and having an adventure there, forming an adventurer group or even becoming the center of a harem that may or may not be wholesome. There is room for experimentation, but as a whole, the isekai genre is remarkably consistent given the genre's youth and expansive size. The problem is that for some anime fans, this is too much in too short a timeframe.
Any anime fan can appreciate the novelty of a young man or woman waking up in a fantastic new realm filled with magic and monsters, but any novelty can become trite and exhausting if it's overdone. In the early 2010s or so, the isekai subgenre took root and rapidly grew, and light novel authors and animation studios all eagerly jumped on the bandwagon. Many series were conceived and published simply because they were isekai, and the genre became saturated with unusual speed. Isekai continues today and is represented in almost every anime season, but some fans have had enough.
Sheer fatigue may be reason enough for some fans to start resenting isekai and calling the genre trash, but there's more. Many of isekai's detractors note how some isekai shows are only popular due to the genre, and these series might even cut corners or coast on their genre's popularity. If the novelty of isekai isn't on a given anime's side, then that series may be exposed for the lazy cash-grab story that it is -- as isekai detractors would argue -- and of course, such an anime is "trash" when judged by its own merits.
A proper story must stand on its own, regardless of fads or trends, or else the anime becomes a product of its time that may age badly in the near future. Classic anime shows are beloved because their themes, characters, messages and emotional impact are resonant in any time period, regardless of contemporary trends.
How The Isekai Genre Can Shake Off Its Bad Reputation
There may not be a single convenient solution to this mess regarding the isekai genre, but some steps can or already have been taken to salvage the genre's reputation and help create more meritable anime series well into the future. To begin with, some isekai titles go beyond the basic conventions of their genre and focus more on traditional literary genres once the protagonist arrives in the next world, rather than generic fantasy adventure stories. My Next Life as a Villainess is a rom-com reverse-harem series, for example, and may appeal more to fans of reverse harems and shojo romances than isekai.
The isekai genre might also save its reputation by simply slowing down the release of new material and being stricter about what's published in anime and light novel form. This will combat the fatigue and allow the novelty to "recharge," so to speak. That restrictive funnel approach may also cut back on the "lazy cash-grab" aspect of the genre. Creators may hesitate to jump on the bandwagon if there are only a few seats reserved for the best of the best.