Second System Syndrome

Definitions

Fred Brooks’s observation that designers often overload their second major system with every idea they regretted leaving out of the first, producing unnecessary complexity. The phrase is used as a warning against unconstrained ambition in rewrites and next-generation platforms.
In plain English: The tendency for a second big system to become overly complex because people try to include every idea at once.
Example: "The rewrite is showing second system syndrome: too many optional modes, too many abstractions, and no clear user story."