I can understand that to someone not used to this, any gap at all might be troubling and one might tend to exaggerate it as "massive".

However note that these walls are fairly thick which narrows any visibility angles considerably. So to really see someone through the gap you would have to be at exactly the right angle and looking straight at them. Sitting on the toilet in one of these you can see some really narrow strip of the sinks area which also reflects the areas in which someone would have to be and looking straight at you to see you. People at the sink area have their back to you. People walking past them to another stall, are not looking to the side.

I'm not trying to convince you that they are ideal, or that your should like them, just that when the gaps are pretty narrow it is not as big a deal as you might think to get used to.

Again this is assuming these gaps are pretty narrow. I get the impression from what some Americans have said in other discussion that in some places they are quite a bit wider than I am used to, and what I said above may no longer apply.