Just a shout-out to esbuild:
I've been working with it and, while it does have a few rough-spots occasionally...in addition to how fast it is, I love how easy it is to work with and write unique behavior for as necessary.
I never really fully digested Webpack, and I think part of that was because of the way it pushed its plugin ecosystem. By contrast, esbuild's plugin system is super easy to understand and placed front and center with the ecosystem off to one side, so if you write a esbuild script (in js OR Go), it's really easy to just write code to do what you want to have done instead of hoping that a bunch of third-party plugins can work together in the way that you want.
Anway, I haven't used swc, but I agree with your assessment. I look at all of the projects that are being worked in that rely on esbuild and swc and they all point to really pleasant development experiences that also have the capability of producing performant code.
What I haven't looked at recently is some of the other language specific pipelines. Is anyone here using non-TypeScript compilers to target JavaScript (like Kotlin, Scala, ClosureScript, ReasonML/Bucklescript) that could speak to the dev experience of the toolchain in 2021, as well as the resulting performance of the js? I'm pretty happy with TypeScript and get happier with each new release, but I'm also really interested in hearing other perspectives about language toolchains targeting js, and what folks are building with them.