Sorry to hear that. What degree? Yeah, most university assignment is just "what the class instructor wants." Not blaming you personally, but in most take-home assignment, it is more efficient to just come to office hours, pretend you don't know anything, to get a gist of what the person on the other end of grading wants. It's the limit of written communication that sometimes people just misinterpret what the other person wants.

I'm in academia and it does not get any better. The system does not reward rogue scholar who leave it to last minute and do what he/she/they wanted. For a proposal in my field, half of the proposal writing is corresponding with the program manager (in my case, NSF) trying to decipher and understand what they wanted within the scope of the RFP (request for proposal) and tailor your proposal towards that goal. I've been a co-principal investigators in many proposals where the principal investigators left the proposal to last minute, didn't kiss ass/correspond to program manager, "misunderstood/misread" the RFP call and goal and got a perfectly solid idea thrown out because it is "outside the scope of the call."

Within framework of a class, with some instructors you can argue about a grade not from the perspective of the assignment, but how you see and interpreted the assignment. Sometimes you can get an understanding instructor that see it from your POV and get your grade rectified if you have done enough work (even though it is the wrong work)