And it possibly still can. There is mentioned in that link of the theory being controversial due to automation, where there ends up being less workers and more production.
napkin math. Say we start with economy size A and a year later we have A+P. The profit rate is P/A. Whole economy-wise the P comes from people doing/producing something. Next year same people doing the same would produce the same P. Thus profit rate fell - it is now P/(A+P). As a result we can see that the profit rate can be increased by increasing output - ie. P(next year) > P(this year) due to productivity increase (thus automation) and/or labor force growth (population growth).