You are absolutely right. SaaS is basically a business of monetizing "friction" between humans. If AI removes the friction, the business model evaporates.
But here is a perspective from my culture: We have a word called "Tema" (手間). It translates to "time and effort," but it implies that the act of taking time is what creates value/trust.
In the efficiency-obsessed economy, Tema is considered a bug. We use SaaS to kill it. But if AI automates all the logical work, I believe humans will start paying a premium for "High-Tema Activities."
Things that are intentionally inefficient. Handshakes instead of Docusign. Physical retreats instead of Zoom.
The collapse of SaaS might force us to realize that "Efficiency" and "Richness" are actually trade-offs. We are just resetting the balance back to the human side.
If there are fewer engineers, then there will be fewer dev tool companies, and fewer managers, etc. meaning fewer Slack, Gmail, MSFT, Zoom subscriptions, etc.
Companies are showing good profits, but if every company downsizes, then every company loses... right?
So, what happens now? (To the economy, lets say.)