I think even more important than learning the mother sauces (though they certainly have plenty to teach), is learning the underlying fundamentals on both a culinary and scientific level. You need to be able to envision how you want a sauce to taste, feel, look and smell (not so worried about hearing) and then translate that into ingredients and execution.
Needless to say this is a lifelong study.
Here's an example of what I mean. I can think of three major ways of thickening a sauce. I'm probably forgetting some. (1) emulsification, such as happens in a vinaigrette, hollandaise, or mayonnaise, in which droplets of one liquid get surrounded by another that can't dissolve it. (2) starches/colloids which interfere with the flow of liquid, such as cornstarch, flour, arrowroot, or all sorts of fun engineered starches (3) reduction - simmering out some of the water so the solids are a higher percentage of the volume.
Each of these methods has pluses and minuses. For example, reduction avoids adding any undesirable starchiness or diluting flavors to the sauce, but requires prolonged cooking or high heat which may change the flavors for better or worse.
I could go on an on! But the point I'm driving at is, instead of trying to memorize a few sauces, you'll do yourself more good in the long run by learning the principles that they rely on so you are free to create and adapt (and fix when things go wrong).