Yes Premillennialism believes in a literal 1000-year reign of Jesus. But the length of this period is secondary to a more foundational issue. At the heart of Premillennialism is the belief that there will be a future earthly kingdom reign of the Messiah from and over the earth in which Jesus and His saints rule the nations and transform every aspect of the world, culture, society, nature, animal kingdom, etc.
This is the fulfillment of the rule and subdue mandate of Genesis 1:26, 28 and the complete fulfillment of all the dozens of promises of the Abrahamic, Davidic, and New covenants which include spiritual, physical, national, and international dimensions.
This is also a period in which Jesus will rule with a rod of iron in the realm of His rejection at His first coming (see Rev. 19:15). The coming millennium is the direct sustained reign of Jesus the Messiah from David's throne (Luke 1:32-33; Matt. 25:31). It involves Jerusalem, the nation Israel, and all the nations of the world. After this Jesus hands the kingdom over to the Father (1 Cor. 15:24, 28) and the eternal kingdom commences. At this time the Father and Son will be on the same throne according to Revelation 22:1, 3.
To me, Premillennialism is not some incidental doctrine. It is an important part of the Bible's storyline and a great source of hope.