OP isn't really arguing against SaaS (after all, OP recommends in the end either Cloudflare or Supabase, which are provided as a service...), that's just the clickbait title, rather OP is arguing against signing up for a hundred different vendors and the overhead of commercial relationships with a hundred different vendors.

Which is... not really controversial. Fewer vendors makes your life easier. Fewer dependencies makes your life easier. It would be awesome if you could build your entire product based on the standard library alone! Sadly... that's not really realistic. Nice pipe-dream though.