I had the same problem last year. I took the whole lot out and planted the best of them and any good sized runners in pots for over the winter. I'm about to clear out a different raised bed that is easier for me to protect from birds and my dogs. When that's done I'll add more compost/soil and replant them. I've got chopped barley straw ready to spread round them to keep them clean, and netting on a frame to go over the top
Strawberries only last about three years anyway, so need to be renewed from runners or with new bought plants
At the very least, if you want to leave yours in situ, you need to take off all the dead leaves and stalks, remove runner baby plants and pot them up for next year, and add more compost round the ones left in place, and a mulch of straw under them