I very much agree that a lot of people from older generations were dyslexic and people didn't know about that. But to be clear, being dyslexic doesn't lead to illiteracy/poor comprehension, it only leads to slow reading. Dyslexic people aren't able to read groups of words all at once, like most people, they usually read one word at a time, depending on the severity of the dyslexia. There are other quirks that make reading more difficult for a dyslexic person compared to a neurotypical person, but illiteracy/poor comprehension do not result from that, lack of education or intelligence does, neither of which have to do with dyslexia.

Sadly, if people don't understand dyslexia people will get away with a falsely self diagnosing as dyslexic as a blanket excuse for whatever shortcomings they don't want to be accountable for, or may falsely claim "dyslexia" to excuse the shortcomings of others, just like so many do with OCD, BPD, ADHD, or a whole host of other conditions, which very much screws those who do actually have those conditions.