And even if you do have a policy of “designing your apps to be SQL agnostic” and you have had that policy for 5 years over dozens of apps. Would you trust your policy enough that you would change your connection string from pointing to Oracle to pointing to MySQL and hope everything would work?

What about all of the programs that you used that depended on Oracle specific drivers. Even in a perfect world where everything was using standard SQL, would the regression testing and migrations be something you would want to tackle as a CTO? Would you be willing to take the reputational risks of something going wrong?