Naah, as long as you can read it, what does it matter.
I start by writing neatly, but by the end it would take a cryptologist to figure out what I've written.
Your Filofax looks loved, full of purpose, and well used. Think of your handwriting as a built in encryption program.
Your Filofax is yours and only yours. It must reflect yourself in the form and content. So as long as you can re-read what you wrote, your writing doesn't matter! Your planner looks used and loved which is the most important.