SPAs are great for the hordes of B2B SaaS apps out there, which for the most part are just some fancy variants of a table. They're not a Photoshop, but they're still highly interactive.

I think the exact opposite is true, B2B SaaS apps don't need to be an SPA to deal with fancy variants of a table. You can create highly interactive UI with things like Rails and Hotwire, sprinkles of JS or even HTMX. SPA's are bloat and often driven by designers who focus on flashiness rather than good UX.