A view from inside (an honest and possibly not popular one)
MH services are good at treating severe and enduring MH issues e.g. Schizophrenia and bipolar, severe psychotic depression, OCD. Things that are largely well defined and that we have evidence based treatments for medication and psychological.
MH services are not so good at personality disorders, adjustment disorder, anxiety and mild depression. These conditions are poorly defined and lacking evidence based treatments and they shade into normal experience.
Many of the determinants of 'mental health' are environmental: poverty, abuse, debt, family problems, unemployment. What can a shrink do about those? Will a tablet solve these issues?? Society has labelled a lot of normal life experience a 'mental health problem' and expects services to solve these but how can we? Soaring divorce rates, family break up and all that can stem from that, cyber bullying, loneliness, zero hour dead end jobs, slum landlords etc etc We need to look far wider as a society (hint: vote Labour today for a start)
People self harm for many reasons and not all people who self harm are depressed or suicidal. Some pills or even a therapist may not be able to help someone who is expressing their distress about bad stuff that has happened/ is happening to them.
Admission to hospital similarly is only really good for treating severe depression, psychosis, mania. It does not on the whole help people with PD. It isn't an environment where therapy can really happen. It can be counterproductive as it just promotes a dependence on short term relief of admission. All the issues are still there when you leave.
Therapy is fetishised. Nearly everyone believes that talking about/ getting proper therapy is the holy grail and will solve all their problems. There is a widespread belief that just talking about past issues will cure them but there is almost zero evidence that it does. It can actually make matters worse. For a lot of conditions tablets are way more effective. Therapy does not work at all for severe depression, psychosis or mania in the acute phase at least.
The evidence based therapies are mainly things like CBT that focus on change in the here and now. You have to be motivated to make a change to benefit e.g. Keeping the mood diary, doing the behavioural experiments. Just sitting in a room for an hour a week might be nice whilst it lasts but it is unlikely to be effective long term unless it helps to develop coping strategies. Of course it is expensive too: an hour of a highly trained professionals time is going to be a limited resource and cost way more than a box of pills. That will always be so. Access will always be limited.
In case you think I am unsympathetic I really am not. I'm just realistic. I am very dedicated to what I do. I go the extra mile for my patients. I am fond of them even if I'm not allowed to show it and I often cry (in private) over the awful things people have told me. So honestly I really do care but it is unrealistic to think that all the ills of society can be helped by ' mental health services'