Worse, it does this broadly and it reduces the learning of actual, valuable "ferreting" skills that every user needs to have these days.
Endless warnings desensitize folks to ALL warnings, including the important ones that they would not have ever been able to recognize by using a few simple steps and skills.
If we can't, just through education, teach people how to take a moment to look at an e-mail message that "seems off" and determine, definitively that it is off, no number of warnings is going to solve the root problem.
If I can teach 80 plus year olds how to do this, and reliably, it's not impossible.