You should probably remove Cinnabar from that list considering that everything Cinnabar does amounts to being edgy and immature, but your point still stands.
The reason why a lot of people are upset with the way the other gems treated Phos, is because we're seeing it from Phos' perspective, which is significantly more human than the other gems.
Phos has a sense of urgency, natural curiosity, and is willing to take risks, unlike the other gems who just grow content with their shitty situation and wait for the pain to subside over centuries when they lose someone.
The other gems likely just thought "we'll let him forget about the pain over the next hundred years and he'll be fine.", which to us as humans is unnacceptable, but that seems to be the norm in gem society. Furthermore, they haven't had to deal with someone who can crush themselves to tiny pieces with gold before. If a gem breaks out of despair they're easy to fix, but Phos' body is unprecedented, and so nobody has any idea what to do apart from letting him cool off over time.
We also know that the gems were, in fact, worried about Phos, if you consider their reaction when AlloyPhos pretended to be genki again.
They were all happy about Phos being "happy" again.
Also keep in mind that the other gems didn't even seem to hate Phos when Phos came to earth for the night raid. Rather they were behaving like adults who are EXTREMELY disappointed in a teenager who has done something crazy, which is surprising considering the gravity of Phos' actions.
That being said, a person doesn't get like Phos if there isn't something wrong with their upbringing, but that's more the fault of Sensei and the nature of the gems itself, than being because the gems are cruel.
In the end, the root cause of everything that has happened to Phos is Phos' feeling of worthlessness, and that's because of the way the gems treat him.