That’s a pretty common theme in terms of “disgusting bathrooms” appearing every now and then in many people’s dreams. But having this type of dream over and over again might indicate it has a more personally specific meaning for you.
Bathrooms in dreams tend to be places where people expect privacy yet frequently experience violations of that privacy (e.g., people walking in on them, the disappearing, etc.).
The disgusting mess in and around the toilets–the usual question is, does that remind you of how you feel about a place or situation in your waking life?
Most cultures make clear distinctions between cleanliness and dirt, which more broadly can symbolize social norms about order and disorder. Your dream may be tapping into feelings about those norms.

Last night’s dream… I went into a public co-habitated open restroom with many, many toilets. Hard to find a vacant one and when I did find one or more, they were all filthy. The place was crowded and filthy. Up against one wall were nothing but fat, nude men and women sitting on the toilets which were next to each other. I saw a vacant toilet. It was so filthy and I tried to clean it but I just needed to walk out.

This type of dream has recurred throughout my life. Mainly dirty, filthy toilets with unflushed, filthy water in the bowl with many people in the open room using the toilets.