Compilation/transpilation is only part of the work traditionally being done by build tools like webpack and parcel (well, webpack offloads the work to babel or similar). I believe that a lot of the speed or perceived responsiveness with Vite comes simply from not bundling the code during development.

For a long time front end tooling has been bundling your dependencies and code into one or more bundles each time you save your code and then that gets shipped to your browser. Vite on the other hand just transpile the changed module(s) and then ship that over to the browser. This works great because browser support ES modules and module resolution natively now.