The puzzle referenced is why more innovation is no longer rewarded by the market. That’s relatively recent.
The article is NOT about some recent change. Please cite the article if you believe it is trying to solve a puzzle concerning a recent change.
The whole point is that this 2% seems to be robust, regardless of investing or getting more ideas, invalidating the idea that the growth is a simple result of the production of ideas (say making blueprints for a new kind of factory, which can then be copied without having to make more blueprints).
Your citation of the article:
> This is a puzzle! Why would the market fail to reward innovative firms, or, conversely, why does it continue rewarding less innovative firms? Unfortunately, here we don’t have clear answers.
does not refer to any recent change, indeed, it uses the word "continue" invalidating your claim that the puzzle is about some recent change.