Do you learn more out of your comfort zone?

So I am sure I am not giving Magnus or MVL an insight they can use to crush me by saying this, but I am a d4 player and most of the time I go for a setup opening called the Colle-Zuckertort; I know where I am with it, and after using it for a while, I am comfortable with the usual moves, and transferring to other opening against certain defences. It can lead to blocked up, stale positions.

As black, I have been playing the Dutch against d4, and what is known as the Lion against e4 - both theoretically attacking, especially the latter; but mostly they both lead to stuffy, stale positions - the Lion is similar to the Philidor, which I know is nicknamed the Philidraw.

I am not playing at a high level at the moment, and in a way I feel I am being a bit timid really pursuing this repertoire - online (on the other site) most games I play are generally won or lost by who blunders first.

When I was good at chess a hundred or so years ago, I played what I now know is called the Grand Prix attack - should I be bold, and choose some more aggressive things to play now; or is picking my way through what I have now a better learning exercise?