I remember when my older son was 2 and a half he did two mornings a week at a private nursery which was considered very unorthodox as the "laid back" lady who ran it would accept children in nappies, usually boys, as she maintained they would just copy the children who had mastered the art of using the toilet. My son initially wore nappies there for a week or two and was probably dry by 2 and three quarters, which was considered late then, but in retrospect I think I mixed with too many competitive mothers with daughters who were all dry day and night by 2ish. By the time both my children entered the nursery attached to their school at 3 and a quarter, it was expected that all children were completely toilet trained they wouldn't have been allowed to attend in nappies. That was some 20 odd years ago and I imagine that would have been pretty standard around the country then.
Undoubtedly toilet training some children can be tedious and time consuming but I think most people get there in the end, albeit with the odd accident. Taking disabilities out of the equation, I wonder why some parents are finding it so hard to follow through on such a basic task it seems to suggest that this is a new phenomenon, I wonder whether we had less distractions can't help noticing how many mothers seem more involved with their phone than their child.