I have heard many piano teachers talk about the order in which Bach's repertoire should be studied... I start with a summer teacher soon and I am looking at new repertoire. I have never played a prelude and fugue or a suite. Some people say you study Bach in the following order: Inventions, Sinfonia, Suites (French then English), The Well Tempered Clavier and Partitas. Some people say after playing inventions you should start on the WTC and then suites. Where does the Italian Concerto fit in? ... I think you have to look at the individual student and see what that student needs at that time. What do you think?
I am no piano teacher, nor do I pretend to be, but I definitely agree with your opinion on this matter. From my perspective, the inventions, partitas, and everything in between are beautiful works of art and are terribly difficult to play. I think it's a shame the inventions, sinfonia, and the Well-Tempered Clavier are universally treated as "teaching pieces;" they have developed a certain stigma as a result. Concert pianists tend to avoid all but the partitas, the concerto, and the Goldberg Variations in their concert programs, as if they won't be taken seriously were they to play an invention here and a prelude and fugue there. The work-around our society has developed for this problem? - to program all 15 sinfonia, all six French Suites, or the complete Well-Tempered Clavier in one sitting. Those encyclopedic Gods! They are so impressive! (Fans self.)
Do audiences really want to listen to all six French Suites in one go? One is so beautiful all by itself. A hundred years ago, pianists would even create a small suite of their own, compiling their favorite movements from different suites. Sometimes "simple" and "easy" can be bracing, beautiful, and bewitching.
Anyway - I say, play them in whatever order suits you. If you are so inclined to start the Goldberg Variations now, then go for it! You wouldn't necessarily need to perform the work for another decade or so, but that's beyond the point. The intrinsic motivation of practicing what you love does a lot more for a person than routine exercises ever will.
There's another side of me screaming: "bad advice, bad advice!" Yes, maybe you should listen to your teacher - he or she certainly has your best interests in mind. Just remember, all of Bach's works have different challenges; there is no need to attack and conquer one genre at a time.