Michael Plymel‘s The False Hero series feel like a bit of a mix between Tate no Yuusha no Nariagari and Isekai Walking; it’s got some of the plot beats of the first with the nonsense progression system of the second. Although the first book has the beginnings of what appear to be a slave harem and that terrible skill-acquisition system, which were major red flags, I like overpowered protagonist revenge stories enough that I was willing to to see if the author managed to course-correct in the second novel.
Instead, within the first few chapters, they establish the presence of gamified dungeons in their non-game world, further break the already broken leveling system (free skill points for no reason!), and double-down on the slave harem setup. Pretty much an instant drop.
The first novel in Kal Griffith‘s This Academy Extra series doesn’t have any narrative red flags fortunately, but instead has quite a number of technical issues. Quite a number, ranging from relatively minor things like poor formatting making it hard to tell who’s speaking, to moderate ones like an entire chapter being doubled or inexplicably missing quotation marks, to fairly serious ones like inconsistent chronology and references (e.g. the system messages are referred to as both an AI-like entity and the comments of the Reaper who sent him to this world).
Aside from that, my main complaint is that no good reason is given why exactly anyone would ever care that the in-universe series went on permanent hiatus when its author is clearly and repeatedly called out for being incompetent. Just let it die and continue to follow the (allegedly far better) fanfictions at that point.