Except the data doesn't support the claim.

Sarbanes-Oxley passed in 2002 and the number if IPOs climbed between then, in the wake of the dot-com crash, and the GFC six year later, while the median age didn't change much:

https://site.warrington.ufl.edu/ritter/files/IPOs-Age-of-Com...

If your claim was true you'd either expect a decline in IPOs or the age of those companies going up and neither is true during that period.

Now to be clear I'm not saying changes in regulation had no impact. Rather my claim is that regulations plus monetary policy and other macro effects fundamentally changed the structure of the market itself, thereby deincentivizing going public, rather than somehow acting as a break or barrier to IPOs.