From the abstract, the paper’s argument looks to be entirely different and reaches different conclusions than a Marxian TRPF argument. This paper claims that net profit margins have increased over the past few decades (which is certainly true at least for S&P 500 companies) and that the increase is mostly driven by lower interest expense and lower corporate taxes. If interest rates and tax rates can’t or won’t fall any further, then they won’t provide a tailwind to margins, and so corporate profits will grow much more slowly (not necessarily decline!) over the next few decades.

Marxian economists generally speak of the TRPF as a decline in return on invested capital, which doesn’t come into play in this paper at all AFAICT, but they also have a bad habit of confusing ROIC with profit margins, which is what the paper is all about.