The effort required to fix tracking cookies is sometimes astounding, while migrating to another email provider is trivial.

This depends on how well the organization handles change and various complexities. Having great technical staff makes things easier, and throwing money at the problem can also help.

Just to give an anecdote: I've had people crying on the phone because their "solutions provider" could not get TLS to work on their www domain despite spending 5.000 euros or so.