And im sorry if this idea has already been floated before, or if something similar is in place.
First off, its understandable that staff cant step in because if they were seen to do so, everybody who was ever banned would be asking for it and it would be all staff do. But how about this.
Forcus on some of the bigger and popular fandoms out there, the ones that are related to pop culture and likely to get a lot of traffic ( Things like Star wars, the MCU, Jurassic park, Pokémon etc ) assign ONE staff member to be the judge when it comes to ban disputes, let them look at the evidence and decide once and for all what the right action should be. Obviously the staff member in question should be neutral and not a member of the fandom itself, to ensure nobody helps out friends and such.
Just a suggestion. Its what I would do if I was in charge. Plus, it may actually stop a percentage of these arguments we see on community central, there would be no need to take it here if the matter is resolved in the way I suggested.
Edit = plus, I imagine this would actually stop a lot of admins getting drunk on power and going ban crazy, knowing it will be looked at closer, it may also stop trolls from flaming and twisting the truth.
No offence but if that is the case then it is not helping. How about this? And its really so simple im shocked its not already a thing, make it a rule that admins can only ban users for breaking the rules and should the ban be disputed, the admin will have to point out exactly where the rules were broken.
Because as it stands, you have admins who are banning people for simply proving them wrong over whatever they are debating. Do you know how easy it is for an admin to get proved wrong and say right, im banning you for starting a flame war, even though the admins were previously adding to the flame war? Im not saying it happens on every wikia but you know for a fact it has happened and will happen. Banning people for no reason also costs fandom money, probably not enough to make staff care, but if they continue to let it happen, more and more childlike admins will feel safer doing it, meaning more and more people will leave fandom, meaning more and more money will be lost, all because some kid got his ego bruised.
Wiki Managers are a relatively new role and not all wikis have them or even need them at this point of their rollout. If a community feels they would like a Wiki Manager, Admins should contact Fandom Staff to request one.
For example, the ToU says nothing about article formatting, but an admin might ban someone who repeatedly breaks the wiki's rules about this.
Admins also often ban for disruption. I mention this one because the person banned very rarely agrees that they have been disruptive (I am not talking about anyone specific here).
Working out the specifics of a dispute can be a long and difficult process. I know, I've done it many times, and I was on the Wikipedia Arbitration Committee too, so have a lot of experience from that!
But as Robin says, we have Wiki Managers now, who will be more able to look in to situations, and might talk to an admin about a ban. But it would be rare that they would intervene, especially on larger wikis where the admins are likely to be very experienced users who have been chosen by the community.
Generally, admins know their communities, and most are careful and fair. They are good people doing their best for the good of the wiki.