Why do linguists give less importance to the centum-satem division than earlier scholars did?

Earlier scholars frequently viewed the centum group and satem group as a fundamental, primary division of the Indo-European family into distinct western and eastern branches based on their treatment of Proto-Indo-European velar consonants.1

However, modern linguists place less importance on this distinction. While it is still widely accepted that a specific sound law occurred in the dialects that evolved into the satem languages—causing the palatalization of original velars into sibilants—this is now generally understood as a shared innovation or a regional development rather than evidence of a deep, primordial split in the Indo-European language family. The division is no longer considered the definitive classification for the entire family that it was once thought to be.1