I am no wine expert, but I wouldn't say that...

I know that many wines bootled in California and other parts of the world, now have plastic "corks" instead of traditional corks. This is mainly to prevent the wine to smell and taste "corky" (??!!??) if you understand what I mean ... so less bottles (and less money ...) are wasted.
But a plastic cap is totally impermeable ; a traditional cork let some contact (a very small contact indeed) between air and wine. And this is necessary for most good wines to mature/age well.

I guess if you want to know more about that subject, you will have to ask a wine expert (there is no translation for "oenologue" in my e-dictionnary ...).
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Alain