A one-man project starting from scratch is not going to be viable in this day and age.

It's a pet project; it doesn't need to be "viable".

I think this attitude is part of the reason why we have so few browsers. Every time someone tries to start their own browser, even just for fun, a lot of the response is just bitching about how big and complex browsers are and how the effort to start a new one is wasted. It makes it so that people interested in writing their own browser (for fun or profit) are less likely to share about it and probably less likely to pursue it seriously