Outside of simply having opinions, some people voice their discomfort with general system mechanics (I may agree with some of it) being overtunned, people also complain about something outright ridiculous like "dwindling playerbase of less than 500 players" in a game with a crossplay, almost like they are expecting pool equal to street fighter or tekken, which would never happen in current competetive market without some miracle.
Some are still grieving vanilla versus players who keep insisting how the game got ruined or something (this one deserves entire different post to dissect all together). Sometimes it's about lack of certain features which a present in other games and so on and so on.
What needs to be noted is that this mixed result comes from 66% of 48 reviews being positive, which is relatively smaller poll size, so it can look more skewed.
But yeah, just like in anything else, there is something worth to criticise with this game too.

Funny answer - because beatles weren't that good to warrant a sequel.
Real answer- because not in a single side route, on my memory, they address any of the issues that started in those relationships. From the quite obvious cases like sexual assault just getting brushed away, or the whole multiple mental manipulations by Chiaki, or Koharu existing.
Side routes are an addendum to the main 3 characters, which is fine for symbolism, but also leaves you wondering if Maruto decided that the resolutions enough to justify relationships which are built on extremely questionable grounds (suspension of disbelief, I know).
Plus the whole Kazusa's true ending ends up with couple not living down their "betrayal" which is presented almost like a form of PTSD, to the point it becomes so god damn humorous that even in the "happy" ending they are not happy at all, apparently, since they have this little devil sitting on their shoulder everytime they have sex or something. Obviously it is open ended and is hinted towards the idea that they can be friends, but it's just funny that the entire relationship is 1 step away from mental breakdown like that, filled with depression, regrets and outright obsession towards the central figure in the story.

I don't think that, I know that.
He is quite a loudmouth who can't really shut up since he wants to be heard all the time. So certain things just add one to the other, from moments, when he casually says how Japanese people should be grateful to their soldiers after mentioning his visits to Yasukuni shrine (the burial ground for their war criminals); to when he, in same casual manner retweeted typical terf posts about access of transgender people to public bathrooms; the additional fact about how he wrote muv-luv with purpose of teaching younger generation history, but also casually releases side material with alt historical battles making Japanese side somehow sink USS Enterprise instead of being absolute losers. Entire coup chapter trying to reinstate a shogun reign. A single historical figure in MLA just happens to also be the person who was acting on the side of Japan during Tokyo tribunal and has had a monument at the aforementioned Yasukuni shrine. A constant yapper and quite honestly a liar, who never had balls to take responsibility for any of his shit decisions which led to the current state of franchise, which was reached because of his overinflated ego trying to chase the bag. Divorced, sold family land, made bunch of exciting promises of sequels and spin-offs with no actual future in sight for 8 years as of now. Constantly begs for money, the recent example of that is a kiminozo crowdfunding, which was SUPPOSED to be a regular normal release under anchor maybe 2 years ago, realistically speaking. But now it is a crowdfunding remaster for 30 mil yen, which was pumped out in less than a year. A crowdfunding campaign which started as an independent out of anchor project and ended up under their wing anyway. After Evan, the former translator for kikinozo left on amicable terms in respectful to public manner, this fat sack of slime, MONTHS after that happened, decided to throw Evan under the bus on his personal podcast for no reason outside of being an old grump sack of potatoes. A monthly magazine, that you can find on steam? It is not as monthly, as you can see. Sold rights to muv-luv to get the shit anime adaptation of the Alternative which will not be finished, even if there are talks how he supposedly had many offers years ago, all of which he declined, because it was not enough. How true is that I have no clue or interest, but sure sounds more than possible. Immortals, the day one closed servers into one year maintenance? Was essentially approved after some literally random kid went up and said how he could make a better game than they did, and they all just went "go ahead and try" old man himself included.

And after all these years this man writing a single game over and over and over again. He dares to fall back to the thing that made him popular in the first place, while constantly appealing to emotion about how he wants world to read his stories, while asking for fans to financially carry all of the burdens and more. Latest edition of KimiNozo? Pulled from all the stores. KimiIta? Last choice when there is nothing else to fall back to anymore. Patch for KimiNozo? Actively being vague, because he knows they can't do it, so he makes passive jokes directly telling fans to do it themselves. Crowdfunding information was advertised in English only partially and only after people started bringing it up. And whatever else he does nowadays.

He is anything, but a good person to me. A narcissistic walking snake who doesn't care or ever will about anything but his beloved child. Not biological, but fictional.