Did it bother anyone else the way it bothers me that their once beautiful cursive is now block printing that is barely legible?
My daughter went to school for 2 months of 2nd grade and her handwriting improved. Then, not long after she quit, her handwriting went back to where it was before attending school. Apparently "proper" handwriting was just a hoop she was jumping through, not something she needed for herself.
My husband just taught a class for 11 yo schooled kids. My 11 yo daughter's handwriting was similar. Better than some, worse than others. (Though she doesn't do cursive.)
Please reassure me that they will catch up to where they were and beyond!
They'll handwrite the way that is most useful and meaningful to them.
If it's not a race, is there a need to catch up?
What is the reason for legible handwriting? So we can read what we wrote. So others can read it. If kids feel it's important for others to read what they're writing, then they'll write so others can read it. (If they're leaving you notes about where they are, then it's reasonable to tell them you need to be able to read the note. That doesn't mean they need to "improve their handwriting". It just means the note has a purpose and writing legibly serves that purpose.)
Otherwise, if they're writing for their own pleasure, the important part for them is getting the thoughts down on paper. It's their project satisfying whatever internal needs they have. They may show it to you, but the purpose wasn't to create something you can read, so you being able to read it isn't important. Though certainly ask questions about what you don't understand so they can explain it. Work on understanding the idea rather than understanding the presentation.
Maybe look at what they put down on paper as a window that lets you peek inside their heads. If you focus on how poorly you can see through the window, it's likely they'll just pull the drapes across the window so they don't have to be bothered by you nattering on about what is just a side effect of having ideas.
Anyone can go through the mechanics of making something look nice. One of the great successes of schools is getting kids to present other people's ideas in a nice package to make it look like learning is taking place.
Real original thinking is chaotic and messy. It doesn't test well. It doesn't look nice. So it doesn't fit well with the factory model of education.
But it's the ideas that are the hard part. Don't worry about the presentation. They don't need to present anything yet. What they need is an environment that is supportive of their ideas.