Netero had might and wisdom, but he was kind of a jackass.
Like when he hired Pariston as his VC because it would be interesting, or when he chose Saiyu as a Zodiac while probably knowing he's a Beyond supporter too. During the chimera ant incident, Pariston's faction putting incompetent hunters in charge of rounding up the stray ants probably caused hundreds if not thousands of unnecessary casualties.
Or when under his reign the hunter exams seemed to be designed with entertainment value in mind, with no regulations in place to prevent nen users from slaughtering the other contestants the Association keeps nen a secret from, not to mention the insanity that is giving people like Hisoka and Illumi hunter licenses. It was bad enough that reforming the exam was a point people tried to use to get votes during the election.
Or when there were ways to instantly exterminate the chimera next and later Meruem's group, but he chose a prolonged campaign followed up with a surgical strike on the palace so he could get a 1vs1 against Meruem, which allowed for hundreds of thousands of East Gorteau civilians to die in the meantime. The team going up against the royal guards would also have been certain death under normal conditions, and Netero even wrote them off as dead during his talk with Meruem (although this could have just been a bluff)
Not to mention that Netero risked the possibility of Meruem killing him at the palace, which would have instantly killed the team and millions of civilians outside when the heart nuke went off.
Netero was a fun guy and I like him as a character, but he was a beyond selfish grade A asshole that the Hunter Association is probably better off without.