I don't believe this, at all. A JavaScript library abstracts away frustrating details that aren't related to the JavaScript language: like insane browser bugs.

Instead choosing a good library can give you free range to explore the advanced programming concepts in JavaScript, instead. jQuery, for example, is highly functional. It makes heavy use of lambdas and closures - even encouraging newbie programmers to use them.

If you want to get better at programming, through programming JavaScript, then a library is the only way that you'll be able to keep your sanity and make that a reality.