Could you explain that part to me because because I’d guess at at least 150 man-years to get a PoC.
Servo was started at 2012 and I think it had full time employees so it’s at least 8 man years to get to that state (I’d guess it was a lot of people in the team, but as a minimum).
Webkit: [1] It's a thousand times easier to compile and was the original base for chromium
Servo: [2] This is much more recent, I haven't looked lately (until today) but it looks to be making rapid forward progress
Elinks: [3] and friends, these are more capable than you'd think (hackernews works, even if you don't build it with javascript enabled.)
Also it's surprisingly easy to write your own engine, it's just keeping up with some of the more political stupidity/abuse is hard.
[3] http://elinks.or.cz/
[2] https://servo.org/
[1] https://webkit.org/