I believe Shinji didn't heed his own advise he has been the only one to cut Aizen thus far he took Aizen to lightly and wanted revenge. In stead of using his mask and taking Aizen's head. All things aside his Shekai really boss second to Aizen in my opinion.
The reason Shinji had to explain his zanpakuto was so that the reader could understand it as well. If he didn't we would have no idea what was going on.