Catia R21 ((free)) ◉

R21 is the last version where you owned the software and the data entirely. There is no telemetry phoning home to France. There is no "cloud collaboration" that leaks IP. It is just the geometric kernel, the user, and a massive assembly of a landing gear. CATIA V5R21 is not beautiful software. It is utilitarian, harsh, and unforgiving. It has a dialog box for every action and a tolerance setting for every surface. But it is also the last version of a dying breed: a pure, offline, mathematical engine for describing the physical world.

A masterpiece of industrial maturity. No longer relevant for new greenfield projects, but forever immortal as the standard against which all stable CAD is measured. catia r21

Because Many small defense contractors, automotive suppliers, and tooling shops refuse to move. They have a library of macros (VBScript automation) written specifically for R21 that will never run on the newer platform. They have Knowledgeware rules that would cost $500,000 to re-engineer. R21 is the last version where you owned