Any non-native English speakers feeling like: So is that why we need to suffer a lingua franca that does not map 1:1 spoken and written? This must be the world's largest tech debt. :)))
Any lingua franca will end up deviating in pronunciation from how it's written. For example, Finnish is said to have very shallow orthographic depth (the technical term for this phenomenon), but you can imagine if people from across the world began speaking and writing Finnish that over 100 years you'd end up with different accents and different variations of the original Finnish. The language would branch and merge…
Written Finnish is mainly a written thing, and while there is a close correspondence between the orthography and how it would be read aloud, when Finns actually speak they use spoken Finnish (puhekieli), which isn't standardized and varies from region to region.