Many early Christians were also Premillennialists, and Augustine was once one, before he switched to what Rome now holds which is largely an Amillennial view. So if we look outside of Scripture, then which best represents the eschatology of Christ? Premil or Amil? (Sorry Preterists, you weren't well represented back then) We stick with Sola Scriptura because God doesn't change, and neither does His revelation. The inspired texts locked in time serve that purpose well.
Truly, Catholics adjust Scripture to fit their beliefs. Protestants adjust their beliefs to fit Scripture.