This. It is known as acquiring taste, and mostly takes time and effort/research. I would also add that 'any' music you haven't heard before is new music, it doesn't have to be freshly minted to be new or relevant. As someone be mentioned above about the Italian 60'/70s scene it was a hotbed of creativity that's still being discovered/unearthed today, I've spent years digging through certain areas of music and still get surprised decades down the line.
Well, as we age there tends to be an accumulation of experience, so it's also to be expected that it becomes more rare to come across a genuinely new experience in everyday life.