The SerenityOS people are implementing their own browser. It's nowhere near usable for the modern web yet, but it's slowly chugging along, inching closer.
Of course the difference between building an OS and a browser is that for an OS, you just have to build something that is usable, how you get there and what that looks like is up to you, and you can really get creative with it and break norms.
For a browser engine, by definition, you have to build something that behaves basically exactly the same as any other modern browser. So you're implementing a gargantuan spec to a very high level of precision (since you have no control over how it's used), and the end result is a technical feat that's only impressive in the fact that it was done, not in that you get to use it now, and it does anything a reskinned chrome wouldn't do.
Of course the difference between building an OS and a browser is that for an OS, you just have to build something that is usable, how you get there and what that looks like is up to you, and you can really get creative with it and break norms.
For a browser engine, by definition, you have to build something that behaves basically exactly the same as any other modern browser. So you're implementing a gargantuan spec to a very high level of precision (since you have no control over how it's used), and the end result is a technical feat that's only impressive in the fact that it was done, not in that you get to use it now, and it does anything a reskinned chrome wouldn't do.