> Pronouncing never heard before words is practically impossible today.

Pronunciation rules do exist. They're not perfect but if you know them you'll get the right pronunciation most of the time. The problem seems to be that they're rarely taught and usually just absorbed through exposure. Most people aren't even aware of them and just do it automatically because of that.

For example, a common gotcha word is "'ghoti is pronounced 'fish'" - except it's not. Ask a native speaker and it's nearly guaranteed they'll say something like "go-tee" or "go-tie", because to get the "fish" pronunciation you have to break multiple English pronunciation rules: The "f" sound for "gh" never occurs at the start of a word, and the "sh" sound for "ti" requires a vowel after it. The "h" also prevents the "g" from being pronounced like a "j" when it starts the word. I can't remember if there was a rule violation for the "o".

Here's someone's attempt at organizing and formalizing them: https://www.zompist.com/spell.html