I know only a few programming languages / environments really well, and really only consider myself an expert at C# and T-SQL.
BUT I have total trust in my ability to program in any language / environment.
Mind you, I will cuss and curse the originators of stoopid systems and framework as I work in them, and it may take me 400 times longer than other people, but it won't be "beyond" me.
Imposter Syndrome does goes away.