ExpressoTS v3.0 introduces major enhancements including reduced dependencies, an embedded environment management system, a new @expressots/shared package, a micro API template for scalable microservices, streamlined application structure, and rendering engine support for EJS, Handlebars, and Pug via plugins. The update also features a new plugin system, CLI improvements supporting npm, yarn, and pnpm, and improved testing via Jest. Additionally, it includes heightened security measures, thanks to Snyk Health Package Ext.