I think it is crazy to do just one work, but there are exceptions, and the WTC is one of them. It is the one of the important works in the world to develop your keyboard technique, the Old Testament in my mind.
But it looks like you are getting musically strangluated without ever playing anything else for your teacher but prelude after fugue after prelude after fugue zzzzzzzzz. There is a ton of technique and music interpretation to learn from WTC. THe very basic note qualities/touches, tenuto, staccato, legato accent all are extensively used in Bach's music. The reasoning for inclusion of dynamic (which Bach often didn't write at all) and phrasing (the breath of your music). Bach helps us a huge deal to interpret music, why naturally the sound rises and falls, why we should naturally phrase the music in a certain way etc. Also how tempo marking changes character in sound much more than actual speed of the notes.
WTC is a gold mine for learning if you know what to look for. If we get tied up only with notes and playing them smoothly it is a dead zone for sure.