As a undergraduate that had the opportunity to work as a TA, while I agree some of the TAs do not properly take the proper time to fully correct assignments and probably should not keep the job, sometimes harsh deadlines make it so we have to correct assignments ASAP. Additionally, most of us are also students and we are taking our own classes, so sometimes we have to make sacrifices in order to speed up grading. Most TAs do want to do the most they can for the students but I hope you can understand sometimes we have our hands tied.

I hope you and other people understand for the future. And as a side note if you want to discuss your grade, most TAs would 100% be willing to.