I don't think the episode is overrated. I think it's so commonly discussed people see it as overrated?
As someone who has dealt with plenty of death, I think it handles it from different perspectives quite well.
When Tara says "It's always sudden" this really hits me personally. My grandma had been in and out of the hospital off and on for years, so the last time she ended up in the hospital, I thought it would be like any other time when she would come home. She died in the hospital, and while she was older and I expected it eventually, it definitely was sudden. It will always be sudden because you can never have enough time with someone you truly care about and love.
For Tara personally, it makes sense for her to not be overwhelmed with grief over the loss of Joyce. She knew her the least amount of time. I truly believe her confession of already having lost her mother, and then telling Buffy to not be sorry is a very normal reaction. She's supportive but not making it about herself, which I feel like so many people do when it comes to loss.
Buffy's reaction is equally painful. She's in shock and denial over the loss of her mother, but still has the weight of the world on her shoulders; not only as the Slayer, but also as a sister, friend, and girlfriend. She simultaneously loses her mother AND is forced into adulthood even more so than before. It's almost like she doesn't get a second to grieve. Combined with the fact her mother was on the mend after already dealing with a serious illness makes it all the more surreal. It's essentially the calm after the storm, but it led right into another storm.
Giles' reaction is genuine due to the time he spent with Joyce. While the two had their disagreements, Giles also spent an entire summer working with Joyce to try and find Buffy. Then we obviously have the events from Band Candy and any awkward encounter afterward. His emotions are tied to those memories.
Xander and Willow obviously grieve for Joyce because they knew her longest from the core group and spent time at Buffy's house. Xander punches the wall because he no longer knows how to cope with his emotions, so violence and rage seem like a way to feel better. He even says he feels better for like a second. Willow changes her clothes because she's uncomfortable. She doesn't know how to act, not only in regards to death of a loved one, but also around Buffy. Willow's parents are still alive; she's never experienced such a loss. How can she possibly comfort her friend in her time of need?
Dawn's reaction is justified by the fact Joyce is the only constant in her life. It can be argued Buffy is the same, but Buffy has a whole other life to contend with due to being a Slayer, and their age gap puts a strain on their sisterly bond. Although Dawn is the key and knows it at this point, Joyce is the only person who has ever loved her unconditionally. Dawn even overhears Joyce saying how Dawn feels like theirs and they need to protect her. To be going through such an identity crisis and the chaotic changes of a teenager along with the loss of a parent is incredibly difficult, and that's putting it lightly. Her entire world has shifted.
I see so much hate for Anya's reaction, but it's one of the most touching, realistic scenes in the entire episode. People can argue all they want about how Anya has been alive for a thousand years and should be quite familiar with death, but she hasn't experienced death as a human; least of all for someone she cared about. Maybe we didn't see those moments on screen, but I think it can be implied. Anya's reaction is awkward because loss and grief often are for those who haven't experienced it before. It's the unknown. And quite frankly, I think her explanation sums up how many people feel about death. It is stupid. It is mortal. It's the not being able to understand how a person is here one minute and gone the next.
And the comments about Spike? Why wouldn't he grieve over Joyce? When she first met him, she had no idea who he was, but even when she learned the truth, she treated him with kindness. She treated him like he was a human, even when everyone else only saw him as a monster.
The point I'm making is everyone grieves differently, in their own way. At the start of the pandemic, a friend of mine took his own life. I hadn't talked to him in years and always thought I would run into him somewhere as we did in the past. I struggled with his death, had a lot of thoughts, but more importantly, I grieved the person I lost personally. Each person means something different to someone else.