I'm 66, when i went to school at 5, i could read, form letters, definitely use the toilet, could listen, pay attention etc & i do not remember any child in my class having toilet issues.
my son went to nursery school age 3 [he was definitely ready] he could use the toilet, could pay attention, he had begun to read [although had some difficulty as he was diagnosed as dyslexic] most children are ready for school earlier than 5, many are ready from 3 onwards. children are always eager to learn, hence all of the 'why?, how?' questions. children do need to play, but learning can be & should fun too. I worked in schools, and early years education was fun for the children. As educators, we worked hard to ensure that learning was an enjoyable exercise. Also all of the children i worked with were toilet trained before school. Educators are not there to teach how to use the toilet, to change nappies, or to teach how to use a knife & fork, those are really the duties of a parent, or whoever is designated as 'in loco parentis'. All children should be toilet trained, & be able to use a knife & fork before being enrolled in school unless there is a reason [statemented, learning difficulties etc] Other than those reasons, i think parents are ducking their responsibilities, & failing their children before their children have even had a chance.