Haha so true. I keep forgetting that... I take browsers for granted sometimes.
Minimalist, modern web browsers exist. A good example of this is surf [0], which is based on WebKit and is <50kb of C. That's less than half the size of React source. It obviously doesn't have all the features that Firefox or Chrome might have, but demonstrates that browsers don't have to be bloated.
Yes. It's called a web browser.
The additional complexity of react is a drop in the bucket compared to the complexity of the undertlying platform.