The rain had stopped prior to us reaching the narrow parts, so it was not slippery on May 2019 - wet, for sure, but in a nice way! Improvements have been made since I walked it, so I assume it’s only become better. The few pilgrims I have spoken with who made it over the summit in the last few weeks also reported no issues with the trail.
As others have said, though, the roadway is always there if you are uncomfortable with a section. To skip the entire route, however, would really be a shame (especially the monastery stay with mass and dinner).
Also, definitely stay at the new donativo albergue in Canfranc Pueblo - it’s spectacular! Plus all the usual recommendations: Arres, Ruesta, Lumbier…