At the other end of the spectrum from practicing "scales", there is the growing size and complexity of libraries and APIs. If you only scratch the surface, learn the minimal necessary, then go on to learning something else, then it's hard gain fluency.

On the other hand, you should only be repeating the same patterns so many times before you build something so you don't have to replace yourself again...

Maybe it's an 80/20 mix; mostly repetition, part novel content.