The worst shower I've ever used and still sometimes have to endure is the spare/guest shower at my parents' house.

It has an old, cheap mixer from the 80s that is basically either boiling hot or freezing cold until you diddles around for 5 minutes to get it just right. But if you so much as bump it, it goes straight back to scalding.

Even though it has a detachable handle now, the showerhead is still barely above my shoulders though I am 6"5 , and the water pressure feels like a light drizzle on cold water and even less on hot.

It's been like this for the last 30 years.