Generally, the vast amount of mental health challenges in our society result from people's inability to healthily deal with difficult and unpleasant emotions.
The first issue comes from stigma, people who experience mental illness are quite simply not treated well by virtually most people in society. This leads to people denying there's an issue for weeks, months, and years which exacerbates these conditions. Then the initial knee jerk reaction to immediately arrive at a "solution" for these difficulties is also what perpetuates and exacerbates these difficult emotions. Then there quite simply aren't enough good therapists... The good ones charge $200-500 an hour in the US usually and they don't take insurance. Hence why you're seeing things like eating disorder and anxiety/OCD coaches come about who are usually recovered sufferers coaching others through whatever their treatment was.
Most successful treatment for something like depression, eating disorders, substance abuse, anxiety/OCD, insomnia, etc. involves addressing and changing beliefs (cognitive) and then changing behaviors (behavioral) which is essentially the framework for Cognitive Behavioral Therapy (CBT) which is the primary therapeutic framework from which most effective therapists base their treatments. A big part of this is learning to live with, accept, and even embrace difficult emotions like despair, panic, anxiety, sadness, grief, loss, anger, sadness, guilt, shame, etc. The habituation model is the process by which your body acclimates to these difficult emotions, similar to being in a cold ocean... When the cold no longer bothers you, the ocean didn't get warmer, you just got used to it. Mindfulness and exposure response prevention are the best techniques for pursuing habituation.
The likelihood of the average person who is sick with mental illness and navigating an imperfect system and exhibiting the ability to find and commit to good treatment, do the work no matter how hard consistently and do this with a good mental health provider's guidance, is low. All in a society rife with biases, prejudices, and priorities that foster and perpetuate mental illness on a broad scale.