First time reviewing something like this so please cut some slack.
Idea of the Story
The idea is definitely interesting, with the MC being transported into what is basically another race, that in many ways is different to humans. Right now, by chapter 19-20 ish we are just seeing what makes him and his siblings Gods different besides long lives and power to humans: domains and how these affect them. In canon in PJ, it is stated by multiple people that Gods are affected by their power more than the demigods, even they themselves sometimes explain it, and right now we may be saying "it's a plot made poorly just to bash or make MC suffer" or whatever, but we are seeing differences from canon, from the MC looks to his personality to the OG Poseidon, and how these affect the characters. The plot with Hestia seems farfetched, and it is, but as a writer I can tell that these are moments where the MC is subjected to situations so that he can respond according to his personality. The idea here is that Gods are individuals that, besides being basically kids with power, they are also being affected by their powers as Gods, and the individual is clashing against their own power.
Characters
The characters are basically newborns at this point in the story, where they get offended easily, do not think things through, and morals and ideals are pretty basic, "this feels good so it is great to do so again and again" or "I don't like this so I want it gone", and we may bash the MC, but he's just a teenager as well, we are expecting maturity from a bunch of kids in the care of a mother, who has been stated to being broken (who wouldn't after seeing their children eaten 5 times by their husband), and who have powers to do what they want, it's impossible to really get it, and the MC is expecting that from his siblings. If the author develops this and their individualism as characters and Gods, then this story will be greater, in my opinion.
Quality of Writing
It's nice, minimal to none grammatical errors, occasionally some missing words, but the idea is generally conveyed.