I don't get the Cairngorm hate

I mean, I understand where it's coming from. I just don't think it's justified.

Look at it this way:

Your only lifelong friend (Ghost) sacrifices themself to save Phos from their own recklessness. You dedicate your existence to protect Phos so that their sacrifice doesn't go to waste.

Ignoring your dedication, Phos remains reckless and gets their head stolen. You decide to sacrifice the remnants of your only other friend (Lapis) in order to bring them back. Still, with Phos being knocked out, you are left alone on winter duty for a century.

After coming back, they almost immediately go back to reckless and lose Lapis' hair. Then they decide that they still want to solve death, so they coerce you to help them get kidnapped by lunarians, not even stopping to consider for a second that you might miss them.

They come back and urge you to go to the moon with them. You have nothing to lose, so why the hell not.

And then after an existence filled with loss and loneliness, you meet someone who actually seems to care about you, is immortal, reciprocates your affection, and teaches you to choose for yourself rather than fulfilling wishes of those who have passed or abandoned you. Of course you would choose him over someone who neglects all their relationships and shows no signs of stopping.

Cairn's abandonment of Phos, even if unnecessarily venomous, doesn't even begine to compare to Phos' abandonment of Cairn.

Cairn's fatal flaw was dedicating themself to people who took them for granted. Phos fatal flaw (among others) was being too scared of loss to accept affection. I don't think either are to blame (which is what makes this story such an effective tragedy.) But out of all the characters people hate in this subreddit it feels like Cairn takes the disproportionate brunt of it.