I grew up speaking italian, which has basic vowel sounds, but effectively no difference in length.
Learning to hear the difference between ship and sheep took me a long time, and it's the same for everyone I know.
Most of my friends who are not regularly exposed to english still fail to notice it or pronounce it.
The same for learning to hear the difference between "a" and "o" in hungarian.
Of course everybody can learn to hear, but it's definitely non-trivial. Your brain just isn't wired to look for the difference, even if clearly the sound is there.
Curious episode: there was this story about an American woman who came to a public office where I lived here in Italy asking about a place near the seaside, and really couldn't understand how the employee would continue using the word "bitch" so freely... it took them some time to clarify that he was referring to the beach :D
That happens. I had a colleague (here in Finland) who in the 1990's happily and regularly e-mailed English colleagues with a greeting "Hello gays" instead of "guys". The English, not surprisingly, never corrected him.
Learning to hear the difference between ship and sheep took me a long time, and it's the same for everyone I know. Most of my friends who are not regularly exposed to english still fail to notice it or pronounce it.
The same for learning to hear the difference between "a" and "o" in hungarian.
Of course everybody can learn to hear, but it's definitely non-trivial. Your brain just isn't wired to look for the difference, even if clearly the sound is there.