It is an interesting question…
I recently made a wee storage unit for one of the classrooms from an old piece of laminated board that, going by the band names on it, was from the mid/late eighties. The pupil’s handwriting was very neat, as were the sketches and graffiti.
I suspect we’re all of an age here where we were initially taught to write by our parents, who themselves were taught be theirs, etc. Sadly, and certainly at the school at which I teach, that is predominantly not the case; when I started teaching some 15yrs ago the state of kids handwriting was a huge shock. They certainly don’t seem to focus on it at primary schools, in my experience… and anecdotally I would suggest pupils with better parenting do have better, neater handwriting.
Human physiology is evolving; where we once used hand tools and the pen and pencil we became more adept at typing, and then using a mouse, and now swiping and tapping. The Royal Society of Surgeons has notes a change in dexterity in its students:
https://www.bbc.co.uk/news/education-46019429