Hi, author here. I'm going to ignore the personal attacks and simply point out that my dev build processes typically have a startup time of under 5 seconds even for large projects, and a rebuild time of under 500ms. This is with Browserify.
If you are having very slow build times with your existing toolchain, the problem isn't the bundling, which is an extremely fast operation. It's almost certainly going to be one specific computationally-intensive plugin that you either don't need, or would also need if using ESM.