For those making active investment decisions, if your IRR falls below that of a passive index fund, that's evidence you'd do better investing passively. Over 2019-2021 the stock market doubled, which is like a 26%/year return for 3 years.
I started "an experiment" when the stock market (VTI) had dropped but not yet recovered. That recovery saw VTI (the benchmark) soar +53%/year for 18 months (1.53 ^ 1.5). But my experiment was even more extreme, rising +120%/year for 18 months (2.2 ^ 1.5 = 3.26). These cases are also the simplest use case of IRR: no distributions.