Yeah, I was reading the manga week to week while Wano was happening, and I kind of got sick of it halfway through.
Don't get me wrong, there are definitely highlights to the arc. But, it's just so...long. And there's so many characters that get introduced that I, honestly, just never grew to care about that much. It almost feels like a spin-off manga at times, with how much they focused on the new characters. I just feel like if it was half as long it'd have twice the impact.
And while there are highs, I don't think we can deny that it can be disappointing in a few areas. Zoro didn't get to do as much as some people hoped. Luffy's fight with Kaido kind of fizzled at the end, even though the Gear 5 reveal was great. The Oden flashback just went on and on. Yamato's decision to stay on Wano. The ending of the arc is a little weak. Combine that with a LOT of set up to even get to the Raid, and you can understand why some people don't like it as much.
Even the Gear 5 reaveal, as much as I've warmed up to it, was pretty polarizing at the time. It was basically making Luffy into the "chosen one", which he hadn't been up to that point. Sure, he had plot armor, but he still had to work for those last minute powerups. "God Mode" felt like it invalided some of that hard work. Some people really didn't like it, and I understand why.
I am planning to re-read all of One Piece once it all wraps up, someday. Just to see how much of it really holds together on a re-read, knowing everything that happens. And I'll admit, Wano is really the only arc that I'm kind of dreading re-reading. Just due to it's length.
But, a lot like with Skypiea, it probably will be a arc that ages well. We'll probably look back at Wano and say "Oh...THAT'S why we had to spend so much time fleshing this out". It's already kind of happening, with the sea level reveal. I think Wano will become more liked the more time we get away from it. And the more people are able to just binge it.