Apart from the fact that it is isekai harem trash, overloaded to the max with degeneracy, the writing of this series is terrible. The plot feels truly contrived, all the fights have no sense of tension as all I can expect is that the MC will come up with another random trick like 'paralyzing mushrooms' or 'aphrodasiac'.
It is okay for stories to use tricks in order for their protagonists to win fights, many shows do this perfectly, and even some anime and manga with decent writing but not amazing writing can pull it off quite well; chivalry of a failed knight with Isshiki. However, the difference between these stories and reincarnation coliseum lies in the fact there is 1. no foreshadowing 2. wins seem to rely on very specific actions by antagonist and 3. 'tricks' are not discussed AT ALL, until the fight is already over.
Why is this a problem? Well, when a story relies on our 'smart' MC here, and suddenly after his amazingly genius battle he explains with a smug grin on his face, 'well you see, i knew you would open your mouth so all I had to do was spit my aphrodasiac into you and then you would get mad and accidentally buff me!'; it at best seems to even the most elementary of readers, that this is a downright stupid explanation.
Good writing relies on using foreshadowing to give readers the hint of how a smart main character will achieve his win, or excellent use of previous plot elements that were inroduced in the story. Good writing can include some deus ex machina writing for the sake of preserving our characters and the storyline, and this can all be put up to 'chance', 'luck' or a 'coincidence'. But it quickly crosses that line when fights repeat in the same way, when there is no tension to speak of in said fights (I know he will win by using another trick whatever it may be), or antagonists just seem downright stupid. You cannot possibly tell me that 'oh yes it is possible to defeat the magical spatial sniper simply by throwing mushrooms at them', do you think our antagonists do not have brains?
Overall, 3/10. The only redeeming quality is perhaps the degenerate art, but even that gives me a feeling of grotesque degeneracy after this post nut clarity of a reading.