Sadly most people are clueless or really they feel UNCOMFORTABLE in their own "skin" so when faced with a person who is suffering grab at meaningless straws. I am not so sure also they are being purposely rude, cruel but what does come out of their mouths is insensitive. It's the "pull yourself up by your boot straps" syndrome.
I also feel such folks are "afraid" to face a suffering person out of FEAR it could be them someday and go into denial, denial and denial. So they "pretend" all is well with everyone & everything in their world. When it is not.
It's the lucky person who does have a friend or relative who is really "tuned in" to know how to truly help a person suffering from a mental health condition or the heart breaking loss of a loved one. Such empathic folks are secure in themselves and can "give" of themselves to folks who are hurting so badly. I would simply suggest to ignore such insensitivity or - if you are up to it - simply say "you don't understand what I am going through and what you just said is not helping me at all, it's actually hurtful". Maybe, maybe (?) they will then get a sense of their behaviors and wise up for the next time they are faced with a family member or friend who is suffering.
Again, no one truly knows what another person is suffering until they have walked a mile in their shoes.
Hang in and hold on to all who are emotionally and mentally suffering. One small step at a time, one moment at a time. And always, always loving kindness to yourself!! You - yourself - are your own BEST friend.