Are athletes' college degrees discounted by employers and graduate school admissions?
"College athletes" is much too broad a brush.  The kind of double-standard you're referring to is mostly focused on a much smaller group of men's basketball and football players at Division I schools.  These are essentially full-time professional athletes.  A lot of the very best athletes among this group do not stay long enough to graduate anyway.

I also think you're overestimating the value of academics and underrating the value of athletics to employers.  It takes incredible dedication to become one of the best people in the world in a sport.  That's genuinely valuable to employers.

Finally, even in the revenue sports, there are many fantastic students who get good grades in rigorous classes.  I've had great students who are world-class elite athletes.  Looking at the major and the grades gives a pretty clear indication of the level of rigor involved.  And of course there are plenty of non-athletes with non-rigorous majors and mediocre grades.

This last point is especially clear in the context of graduate admissions.  Graduate applications include letters of recommendation and a full transcript. It is easy to see directly whether someone is taking rigorous advanced classes and doing well in them. There’s no reason whatsoever to discount athletes based on the existence of easier classes when you can see what classes they actually took.