We went from “the fundamentals have changed” to “the 90s were a long time ago” real fast. Regardless of who made the point initially you are arguing it. Full redesigns are expensive, inefficient, and likely to introduce new vulnerabilities. The existing implementation is refined by decades of real world use. We can incorporate new lessons without a full redesign - if we can’t then we should stop being software engineers.

A full redesign is usually the type of project a CTO I worked for pejoratively called “computer science projects.”