Previous SiFive cores compete against the A72 (announced but not yet shipping that I know of) and A55/A53 (shipping in the BeagleV "StarLight" beta and HiFive Unmatched and probably unannounced embedded applications).

In the four years since the A75 ARM has announced the A76, A77, A78, and A710 as annual incremental improvements (the most recent of which are not available in products yet), plus in a new higher-end line the Cortex-X1 and X2.

So ARM is not standing still, but SiFive is catching them at approximately two years of ARM progress every year i.e. closing the gap by one year per year.

Its not as far alone as the lower end but it defiantly happening as well.