Here's my explanation of learning differences:
We all learn. But how we learn is sometimes different. Some people have trouble learning to read or write or use numbers, even though they can learn other things easily. Some people are slower to learn everything. And some people have trouble learning to speak, or use their bodies, or understand what others say. Some people even have trouble learning to see or hear. They can see and hear, but what they see and hear doesn't make sense to them. Some people also have trouble learning to understand how other people feel and what they are thinking. And some people have trouble learning how to take care of themselves, or keep their house clean. Some people have trouble keeping track of time, and forget things they need to do.
When someone has trouble learning something, they might need more time to learn it, or they might need to learn it a different way. Sometimes they never learn it, so they have to find a way to do things without using that thing. Someone who can't read might need a computer to read for them, or someone who can't keep track of time might need their phone to help. Someone who can't learn how to walk might use a chair that rolls around. Someone who has trouble learning to talk might use a computer that talks for them or they might use hand signs. You can't always tell if someone who has trouble learning something will be able to learn it, so some people start out doing things a different way and then learn how to do them more easily.
Often people who have trouble learning one thing can be very good at learning something else. Someone might be very good at reading but have trouble with numbers, or have trouble understanding people but know a lot about a favorite thing. Some of the people who have done the most amazing things have had trouble learning.
This might be a nice tool to write text designed for an AAC user to say. I've been thinking of writing some core vocabulary stories, but I find it hard to write if I'm constantly checking a word list to avoid fringe words. I just wish I could adjust it to different vocabulary sizes.
[edit: Just found this, which color-codes words by frequency instead of just banning all words below a certain frequency.]