If there is any barrier, it is not intentional, I assure you. Math is just hard.
Part of the difficulty is artificial.
Whether intentional or not, it's there. I have yet to see a textbook that really taught learners as they deserve to be taught. Some are good in some aspects, but a perfect textbook does not exist.
"Here are some theorems and some proofs and here are some ideas left as exercise to the student". smh.