I think almost everyone with any interest in the club, either directly or indirectly, is convinced of Gus Mackay's gross incompetence and inadequacy for the role he is/has been employed for.
What you probably have to have some direct experience of is the self-serving and borderline evil lies he'll tell to suit himself regardless of the damage he does to others.
You see a bit of it in the flat out lies he talks to places like the BBC in order to promote himself.
But he's demonstrated some real evil in the way he's bullied some staff and players into signing compromise agreements which disadvantage them under the premise that their payments won't be paid until they sign and/or won't be paid at all because "the club will go under". He added to that that if an individual didn't sign, none of his fellow/former teammates or staff members would get their money either as the club would just close.
The disadvantages he forced on people weren't just financial - they included forcing them to sign away rights and provide indemnities to the club for the club's responsibilities.
Faced with the choice of no money ever or no money to pay mortgages, moving costs, Xmas, etc, he took advantage of these people.
That's the reason people aren't just leaving the club, but leaving the sport altogether and there's so much disguised vitriol towards him on social media.