I'm sure those works weren't translated and copied by hand for hundreds of years until the invention of the printing press in the 1400s.
Besides books being taken out for various reasons, words and meanings of the scriptures were changed either intentionally or unintentionally. This isn't a hidden fact.
you’re right, they faced even bigger challenges…
Aristotle’s poetics were initially disseminated oratorically and weren’t written down until much later, so not only do you have a gap between when his philosophical ideas were spoken and when they were written down, you have a sizeable gap between the original copies and the surviving manuscripts…
Julius Caesar’s Gallic War accounts are purported to have been written by Caesar himself, so not only do you have the challenge of relying on a singular author, again you have a sizeable gap between the original texts and the surviving manuscripts…
to your second point, the books that were not included in the canonical biblical texts aren’t inaccessible though…you can easily access copies of books of the apocrypha and pseudepigrapha today and read them…
like i said, there are thousands of manuscripts available today in 2024 that can be cross-referenced with current versions of the Bible, so the fact that words changed during translations isn’t a road block to understanding scripture…the resources available for biblical study/research are more numerous today than at any other point in history, so the “books were excluded and words were changed” arguments don’t actually hold up to scrutiny…