i did a similar audit and the worst offender was duplicated config and generated files across the Next.js frontend, NestJS backend, mobile wrapper and CI. make a tiny MVP baseline you can actually ship from: one Next app, one thin backend service with a single auth route, and move CI/mobile scaffolding into a separate repo or a generator so they don't come along to every new project. consolidate shared types and infra code into a single package, kill unneeded dev-tooling files, and change heavy codegen to on-demand scripts that run when you add a feature. build a tiny CLI that scaffolds a feature folder instead of including every possible file in the base. that cut my new-project file count from hundreds to a few dozen. fwiw i used a starter kit that had auth and payments preconfigured, Vibe Coding Starter Kit, to get a production-ready baseline without rebuilding all that infra.