Romanian and Turkish disagree. And the spoken language still differs (probably less so in Romanian, more so in Turkish).
One can still speak wrong if they learn to speak the letters wrong but chances are reduced. Are Romanian and Turkish similar?
It's more than just sounds. Turkish and Romanian alphabets capture the sounds of Turkish and Romanian alphabets quite well.
But then...
In Turkish "I will do something" is written like this: "Bir şey yapıcaǧım". And if you're going for proper enunciation, that's what you will say. In most situations most people will say "Bi şey yapıcam" (note the omission of "r" in "Bir" and "ǧı" in "yapıcaǧım").
Do the letters correspond to the sounds? Yes. Does it help? Nope, people will not speak the way it's written, because written rules describe a very specific rigid set of rules. And, for example, elisions and contractions [1] are very common in nearly every language and are often frowned upon in written texts (except for a small number of unavoidable ones).
And that's before we go into the plethora of sounds between dialects and regional variations. For example, in Swedish, there's a combination of letters, `sj`[3] that has at least four different pronunciations across Sweden. So, the word "seven", "sju" will be pronounced with [ɕ] in one part of Sweden, with [ɧ], in a different part of Sweden and so on. It's the same word, should it be spelled differently for each group of people?
And note, we're just touching just 1% of 1% of the complexities of pronunciation :) And they rarely if ever can be captured in written text and rules for the written text.
[1] https://en.wikipedia.org/wiki/Elision
[2] https://en.wikipedia.org/wiki/Contraction_(grammar)
[3] https://en.wikipedia.org/wiki/Swedish_phonology#Fricatives Wikipedia has a full paragraph dedicated to this alone
You are basing your assumption on languages using Roman writing system which actually isn't capable of expressing all sounds used within the language. All language systems doesn't suffer this. For example most Indian languages have accurate sound to letter mapping even to the level of defining short and long sounds of same alphabet differently. In order to speak correctly you just have to say the individual sounds together. There is no weirdness involved.