SaaS investing has been on fire the past decade and the returns have been gushing in, with IPOs like Datadog, direct listings like Slack and acquisitions like Qualtrics (which is now being spun back out) creating billions of wealth and VC returns. Dozens more SaaS startups are on deck to head toward their exits in the same way, and many VC funds — particularly those with deep portfolios in the SaaS space — are going to perform well. Yet, the gargantuan returns we are seeing today for SaaS portfolios are…