I recently came across a great blog post by OpenView called "The New SaaS Metric You Should Be Tracking". In short, the argument is that current SaaS metrics are dated and as go-to-market models shift to product led growth we should evaluate these businesses with a new set of metrics. The core thesis is that PLG companies don't have the same immediate growth rates as SaaS companies of yesteryear since they take time to compound.
In the post, they introduce a metric called "Natural Rate of Growth", how to compute it and some associated benchmarks. NRG is essentially a growth metric that removes paid channels such as BDRs, paid ads, events, etc. It primarily accounts for organic, direct and referral customers.