The most important thing the Giants need is alignment. It sounds so simple, but for them it's hard because they are so antiquated and a family business in the way that some family businesses prevent change.
If Judge is your guy and Gettleman isn't, find a GM who can work with Judge and get on your way. Many organizations do it this way. If the relationship is right the two won't care who was hired first or who reports to how, they'll just get the job done. The Giants are still trying to build their team with this separation of GM and HC in an old power structure from 1979 where the owner and his family has the GM's ear. It worked well for a long time as it was aligned, yes, but is now over. They are not dynamic and they are not making good decisions on player evaluations. That's why they suck.
Again, they are 42-75 over an 8-season period with 7 losing seasons going back to when Tom Coughlin was screaming that the lines were not being rebuild properly and the rift between him and the FO at the time was the start of this. He was scapegoated and sent out to pasture. Fast forward years later and it's worse. They have lost 41 of their last 53 games played, the worst franchise in the league. They have had 2 different GM's and 4 HC's during that time period. What has stayed the same? Organizational structure. Adapt or die.