I am so sorry to hear your experience mischance
(Also Apologies as I misread one of your posts earlier and thought you were also talking about a separate discharge of yours (after a slipped disc) but you weren't. )
Your OHs situation went wrong from what you describe mischance. I do hope you raised a complaint with both hospital, health (GP surgery & primary health team) and social care teams, so that they all took action as quickly as possible and also looked into what happened in detail to learn from.
It doesn't generalise that it happens regularly - at least not in our LA areas- as part of D2A process. As said by many PPs, that to get to D2A already initial plans for discharge needs (carer support, referral for nursing support and crucial essential equipment) will have been made whilst in hospital after clinical team assess the person as medically fit for discharge.
Discharge to assess is about ongoing rehab and ongoing assessment of needs with what might be better defined as reassessing or fine tuning by MDT in community settings (because people can be different once at home or out of the ward due to a variety of reasons) and sometimes longer term adaptations will also be identified as beneficial.
Several of us have said it generally does work well, as we see it every working day and we definitely remember and worry about the unusual cases where something didn’t work and want to understand why and how it can be quickly resolved. (Whether it wasn't set up well or that something changed that was unanticipated).
What's important for OP is that - if she suspects her DM is being unrealistic to her discharge team about what she was or can independently manage and what family will support with- if it's related to potential capacity issues- that OP contacts the hospital discharge or s/w team to give them family information and perspective. That can form part of the background information drawn upon in capacity assessment. It is also useful context even if the person is assessed as having capacity. The MCA 2005 has clear processes and statutory guidance.
The other important aspect for OP is to be reassured that there are community social care teams and MDT health teams who all work incredibly hard and can be contacted if things aren't working well at home.
People are wonderfully complex, so no one person (or case) is ever the same nor follows exactly the same path. It's why there are multi disciplinary teams in both hospital and community.
I have a great deal of empathy for people on this forum. Not only being in the field but also having been an informal carer myself on 'the other side'. Those professionals have families too.
If you want to talk about when things didn't work well and how people used to have far shorter prognoses, you only need look back 30 years ago when patients were still routinely moved into long stay hospital wards. The old community care act, superseded by the care act, literally saved a tremendous amount of lives. I used to be in research, still read research papers about improvements to clinical outcomes. These policies have a basis in sound clinical research and continue to be evaluated as that's how policies develop or change.
I don't disagree that we all as a society would love a bigger health and social care budgets though! Who wouldn't? But to do that which other area will money be taken from? Education? Policing? Infrastructure? Armed forces? Those areas equally fight for more funding, as it's all balanced by tax levels which is a much wider debate. When people say they want social care to have more funding, i always suggest they consider writing to their MP as well. Because that's how change of funding priorities can happen when there's an overwhelming national push for it.