The right of way is important, and if there is no genuine dispute about who had the right of way that is a big deal. But, it may not be the whole deal.
Washington courts hold that the right of way is “relative rather than absolute.” Both the favored driver (the one with the right of way) and the disfavored driver (the one lacking the right of way) must exercise ordinary care.
The favored driver may by law assume other drivers will yield unless and until a point a driver exercising reasonable care would realize that the disfavored driver is not going to yield.
Fault is comparative, meaning both drivers could be found partly at fault under the facts of a particular case.
Sometimes fault is cut-and-dried. Sometimes it’s not, even if you have the right of way.