Hi, I would think that a lot of the time if you ask someone to stand outside the shower door you will be fine, in general other pilgrims are helpful. If you suffer from Claustrophobia, some of the dorms may feel overwhelming, there is little room in some. You may do better to stay in Private Albergues, where there are fewer people to a room. Be sure you have your anxiety management strategy ( relaxation exercise, breating, paper bag etc )in place, so if you have a panic attack you know how to help yourself through it. Perhaps have a set of written instructions in several languages, you can pull out, so others know how to assist you if something happens. I am a bit OCD re cleanliness and worried about that before starting my walk, I carried Jandals to wear in the shower and ended up ditching them as I did not want to carry them. I do confess to standing on my heels in a few showers as I did not want the whole of my foot to touch the shower bottom. In France I had no problems. Now I have Crocs Cleo Sandals as my second footwear, which if necessary I can wear in a shower if it looks gross.
Hope this helps, Gitti