After wrestling with Webpack for years, Parcel was just a joy to work with. It actually just works. It's amazing that in 2020 the most common use cases that nearly every front-end developer runs into require an insane Webpack configuration. The only small complaints that I would have about Parcel is that the documentation is a bit lacking, and it would be nice to have just a bit of configuration (coming in Parcel 2), but hey...compared to Webpack I'm not complaining.
I've used it on a couple of projects. It wouldn't be my first choice for a design system, but works well in a large setting and takes advantage of some powerful and popular tools such as React and Typescript. For smaller projects, this is most likely overkill.
Semantic is great if you want to hack together a fully fledged website very quickly. It's very intuitive, and I would recommend it to any developer looking to take advantage of modern tooling.