I’m not exactly a historian, but I do need to read old documents periodically (when I’m writing a podcast episode and reading documents that are fairly obscure and not transcribed.) I’m 50 and know cursive, and old handwriting is still so hard to read! Knowing cursive only helps somewhat imo
I also find it's especially bad if you're trying to decipher notes that were not meant to be shared—I spent a few months going through Arthur Miller's archive and the early notebooks for DEATH OF A SALESMAN were, uh, cryptic—and I wrote exclusively in cursive for a decade!
I hadn’t really thought about it, but yeah, scans of diaries and such can be particularly rough.
The number of times Christopher Tolkien comments on his struggles interpreting his father's handwriting in the early drafts of The Lord of the Rings (and other stories) in the History of Middle-earth books is really a lot, even though Christopher clearly knew JRRT's style better than anyone.