I would poncho up in certain situations, but if it’s going to be quick I’ll hide out. If it’s going to be a complete washout with a river running through the park I’ll exit completely.
Rain is seriously the biggest damper on a trip, far more than sunshine and humidity, IMHO. It’s ok if it’s just for a bit in the afternoon, but it can ruin your day if you’re unprepared. (As I learned the hard way! )
One trip in May (maybe 2018?), it was cold-ish and rainy for every one of our 4 park days. It was alternating drizzle and hard rain continuously all day. I think the sun finally came out on our last day. We went through a 10-pack of ponchos from Amazon and I had to buy a hoodie in the parks that I wore in the mornings every single day. At least I can easily identify all the pictures from that trip!