Even if you don't think Essendon were ever technically proven to be using PEDs, Hird oversaw a program that was at the very least incredibly negligent in it's administration and record keeping, and disregarded the health and safety of the players he was responsible for. Those players will never know some of the sh*t that was put into their bodies by people they trusted. That alone should be more than enough to prevent any club from ever looking at Hird in any senior role ever again.
Not to mention he never admitted any sort of responsibility. Had Hird owned up to it then the entire saga would have been over in a matter of months.