I feel like they attack from the wrong angle. Consider BareMetrics an SAAS. They aren't really just a CRUD, but are lumped in with CRM's. The easiest CRM is a spreadsheet and a mailer like SendMail.

Many organizations have used Excel as a CRM and then hit a lot of problems. It is very hard to scale up and also hard to add features to if you need them.

But they have actually replaced many of the popular services with a crud and also mention that MailGun / Stripe are irreplaceable.