There's a difference between forcible treatment, and being kept in a room wearing nothing but anti-ligature clothing, with none of your belongings, no blankets, no furniture, food being provided through a hatch in a door, etc.
It's great that you've met a couple of people with severe mental illness that had good experience of care - most people do. But it's not relevant to what I said.
Solitary confinement is torture, which is why it's banned unless there's no other option. In the English system seclusion is used far too often, and often as a first not last resort. This is also true for restraint and rapid tranquillisation. There are national and local programmes of work trying to reduce use of force, and we've even had a recent law change to prevent the use of force in mental health units. The new law recognises that people's human rights were being abused.
https://www.legislation.gov.uk/ukpga/2018/27/enacted
https://www.gov.uk/government/publications/mental-health-uni...
https://restraintreductionnetwork.org/
We're reforming the mental health act because we recognise that people's human rights are not respected, and to improve the use of advance directives and reduce the use of compulsory treatment, especially the use of force: https://commonslibrary.parliament.uk/research-briefings/cbp-...