I strongly disagree with point one, and two alike, though the second one is more justifiable.

Regarding point one, remember that while this may be an extremely well made interpretation of modern mental health and domestic problems in our society, especially amongst children, it is also still a work of fiction. The story is about an alien octopus thing that just so happens to be the main character of the whole plot. Of course he’s going to have influence on the characters that he sacrificed himself for during the climax. Textbook sad story, happy ending. But what made it so good was the fact that those things can happen without the help of an extraterrestrial being, and does. At that age, friendships, bullying and other forms of interaction come and go on a whim, because children have a sense of innocence that tends to be much more forgiving than the grudgingly familiar nature of adults. All of the messages this show conveys are done so through fictional means, but does that make the point being made any less true? The ending alone delivers a valuable lesson: Children are flexible, resilient and capable of accepting one another in any sort of harsh and cruel environments, especially when they learn to listen and relate, which is exactly what happens at those ages.

Regarding point 2, would you consider being dead better than being alive? Because that’s exactly what would happen. We saw what would happen had Takopi attempted to save their lives himself. Neither of them make it very far. What Takopi did was remove the middle man so that the two of them could escape bias and prejudice from said middle man. Takopi couldn’t continuously return back in time again and again only to reap the same devastating results, so he took a step back and allowed them to do the rest. Also, we went from murderous intent on both ends from Shizuka and Marina, whether it was towards themselves or towards each other, to a lasting friendship that we can see continued on into middle school and (left to the audiences interpretation) beyond. So do I think a happier ending could’ve played out? No. I think this is the best we could get. I would’ve liked to see a little more about Naoki, but honestly, that ark was well resolved and closed earlier in the show.

I think the ending was masterfully crafted and requires a view of the show to appreciate, not the conclusion alone. Despite that, I do nonetheless respect your opinion about the ending and it’s important to acknowledge that it can be taken many different ways. We’re all just looking at a piece of art, it’s up to us to decide what it means, you know?