Dude, if you watch every episode of the ant arc with a checklist that contains those points that you are referring to, then I pity you since you miss all the other stuff that is happening in the arc.
I don't watch it with some sort of checklist, I watch it with the expectation there is a coherent narrative and that plot elements are resolved. At the moment, the narrative is pretty incoherent.
Killua changed a lot, especially during the fight with the ugly rabbit ant;
That was 16 episodes ago, or 5 hours of narrative ago. Beyond that, it was incredibly unsatisfying resolution. We learn how Illumi's been controlling his brother, and Killua's response is basically "meh, whatever". No anger, nothing. Just moves on, except suddenly he's superawesomeperfectbrillianter. Come to that, how he even finds out isn't really satisying. Rammot was a grunt. In Star Trek he'd been an evil red shirt. The fight wasn't that really hype, it was just a random encounter. But suddenly, this random encounter with fairly generic grunt is the one that makes Killua snap? It just seemed like a lame excuse for a power-up to me.
No? Gon has to realize how weak he actually is compared to many other warriors in the world
We've known that since the Heaven's Arena arc. Heck, even if that was new information, it doesn't take us 30 episodes to work out that Pitou is kinda strong.
and he also learns that not every perceived enemy is entirely evil - they both progress a lot as characters because for the first time shit is getting out of hand in the world of HxH.
Again, Gon already knows not every perceived enemy is evil. He's been kind and forgiving the whole series, it's not like he had an epiphany moment.
I mean hell, even fucking Netero has to come out and prepare to fight against those beasts.
That doesn't even mean anything to the viewer at the moment because I've never seem a demonstration of how good Netero is, I've just heard 30-episodes worth of boring-ass exposition by Morel and Knov. I'd be a bit more hype if Netero had actually gone to town on some fools, but for the last 15 episodes, we've had "and soon Netero will turn up and he's superpowerfulawesomer than everyone". That gets immensely tedious when Netero then doesn't actually turn up in about 5 hours worth of material.
There is a lot of stuff to be learned about everything HxH related, and on top of that the whole Chimera Ant idea is pretty well worked out and just seeing this empire rising is something exceptionally well done. I mean we're watching the evolution of a life form from one lonely and shabby ant queen to a dozens of various beings that evolved to the point they are almost human - it's just fascinating to watch for me.
Why? It was all so pointless. The arc could have been set up infinitely faster to get to the actual core character development, plot development and fight scenes, which are the things I want from my shonen. At the moment, I'm getting basically no character development, absolutely no plot development, and fight scenes every 5 episodes.
And since those things are pretty remarkable, I personally don't mind the change of focus; all the stuff about Ging and those points you've mentioned will come one day or another, but for now I'm pretty happy with what I'm seeing. If you don't like it, then that#s your opinion, but calling it filler is dumb.
Alright, it feels like fan-fiction, then. Whatever you want to call it, I find the quality of HunterxHunter has bombed downwards. At the York Shin City arc, it was basically the best shonen anime to date, now I'm just sitting through episodes bored silly. Right now, it's making Attack on Titan look like one of the fastest-moving shows out there.
EDIT: and if what dan says is true and this arc is about Meruem, why does it take until episode 91 for him to turn up, when the Chimera Ant arc started at episode 76? This is what I mean about pacing.