You accidentally downloaded the modern USSEP (version 4.3.0 or higher) instead of the archived 4.2.5b. Solution: Delete the wrong file and re-download the archived version 4.2.5b from Nexus.
Here is the most critical part of this article. That page only hosts versions for the current AE build. Unofficial Skyrim Special Edition Patch 1.5 97 Download
The is widely considered the most critical mod for any Skyrim player. While newer versions of the game exist (such as the 1.6+ Anniversary Edition), many veteran modders specifically seek out the Unofficial Skyrim Special Edition Patch version 1.5.97 to maintain compatibility with a vast library of older, highly stable mods that have not been updated for newer game builds. Why Download USSEP for Version 1.5.97? You accidentally downloaded the modern USSEP (version 4