> from spelling you can easily infer pronunciation

Usually :) But plenty of cases where you can't, the most common one being silent letters: while you can guess silent letters pretty consistently, some words have unusual silent letters ("asthme", "oignon") or usually-silent letters that aren't silent in this case ("huit").

Some words are also homographs: spelled the same, but not the same word and might be pronounced differently ("content": is it someone happy or multiple people counting?).

Some letters silentness change depending on plurality of the word: œuf and bœuf, the F is pronounced in the singular but not the plural.