> People were writing, including those in Rome and those outside of it, but not all these writings survived into the modern day. Some of them may have been surpassed by later written works, some of them may have been a bit boring and just not enjoyed.

This is an important aspect, literature survives only if it's copied. The widespread use of papyrus meant works had a relatively short lifespan (especially compared to vellum) and unless it was copied, it would degrade until it crumbled into dust within a century. Since everything was copied by hand, the only way a work would propagate itself is if it was popular, if it wasn't it only survives (if at all) in mentions by other authors; Aristotle's Poetics part 2 only survives in mention by part 1 for example, no one else mentions it despite the popularity of the former. Combine this with the switch to the codex (book) from the scroll after the turn of the millennia and you have process which further compounds this with older works being left behind on the older, less dense format. Unless something happens to be deposited in ideal conditions such as with the Oxyrhynchus letters in Egypt (not exactly literature but close enough), literature will only survive if it is copied.