You tend to have to "come to" mindfulness though -- in my personal experience you can't just wander over to someone with depression and go "oh, meditate and you

You tend to have to "come to" mindfulness though -- in my personal experience you can't just wander over to someone with depression and go "oh, meditate and you'll feel better". They wouldn't know why they were meditating or what it was trying to achieve. You need to come to understand the mechanisms in your mind that cause the symptoms before you can take action to mitigate them and that wisdom unfortunately usually only comes with time.