The bespoke school utopia for all, or any child, in the state system, just doesn't exist, it never has.
Schools are there to teach, primarily, not to solve all the student's social, emotional and health problems, they just can't.
It is our job as parents to make sure our children are capable of attending the educational setting the we choose to send them to.
If your child's school cannot, and never will, meet your child's individual needs, look at other schools, beg, borrow money to pay for private and pay it back over years (like a mortgage) or home school online. Not all schools are rigid, but they all do have many other pupils who also need an education in them.
We can all argue all we like but if isn't the funds or trained staff available then the adaptations are just not there.
If the adaptations you think would be suitable, free and easy, for your child's school then get it done in your child's school. Talk to the Head, Governors, other parents. These changes don't have to be across the whole country if they are free and easy they could just be done on a school by school basis. There is no point in waiting for the Government to demand changes, that might take years, even a change in Government, and then still years, by this time your child is likely to be out of the school system.
Do you not think Heads and teachers want to make school as productive as possible for as many as possible? If they thought these free and easy solutions were solutions why aren't they implemented? State education is for the many not the few we all have to deal with that. All parents and all children. No one is more special than others.
If you don't think that some parents use a diagnosis as an excuse to demand that schools do more and they can be excused you are mistaken. And I know it's not all, or even most parents, but some do. And this stretches resources further.