"The plasticity changes as we get older, but the human brains does not lose the ability to learn things, counter intuitive or not."

Perhaps not lose entirely, but certainly age can dramatically reduce the ability to learn certain things. This (rather long) article goes into detail:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2947444/

The section marked "Language Exhibits a “Critical Period” for Learning" is maybe the most relevant.

However, the article was written in 2010, and may be out of date. Understanding the brain's mechanisms and plasticity has advanced significantly over the last few years.