In WA, neither party need to prove any fault for the court to sign a decree of dissolution of marriage or decree of legal separation.
There is no law in WA that requires a respondent to participate in a court proceeding.
Once the deadline expires, the petitioner/moving party presents evidence to the court that the other party has been served as required by statutes and moves the court for a default. The court will grant reliefs that are not more than for what was asked in the petition/motion. This is why it is good practice to be very specific in the petition/motion so that if there is a default, one can ask the court for the specific things mentioned in the petition/motion.
So, the respondent ignoring the court proceeding will not delay the proceeding. In fact, getting a default may be quicker than going to trial.
In Washington, if you have received notice of a civil proceeding and fail to appear, the other party can proceed without you. So, for you, if you have served your spouse and he or she does not appear, the proceeds will occur without them.