@Coruscation:
What worked: The one part of this chapter that was very well done was Kyros. The call-back to his tin eyes that can't cry and how he's fought for Dressrosa's freedom from oppression and control all these years were well chosen. It reminds me of some of Oda's great past moments where a character just lets everything go and cries like a baby, unabated – like Chopper upon leaving Drum Island and seeing the cherry blossom fireworks, or Robin during her famous "I want to live!" moment. I think this is going to come off as an even better moment when the arc sinks in and fatigue and disappointment wears off. One of the better scenes in the arc, possibly.
What didn't: But everything else is just, welp, Oda commited to these characters so hard and so badly wants me to feel for them but I just don't. Rebecca has done essentially nothing but cry for far too long and has almost no personality. Viola was introduced as passionate but for almost the entire arc has done little but run from place to place whilst being protected or served as Oda's recap device. Riku has been, imo, uninteresting and bland for the whole arc. A generic kind gentle king is all well and good, but not interesting enough to carry such a large burden. Can the man even crack a smile if his life depends on it? Gatz, though I don't dislike him,came out of nowhere with no build up and took too much of a presence in climax. Meanwhile the characters that I care about are doing nothing (Cavendish), pushing the oh-so-contrived feeling Birdcage (Zoro, Franky, Sai, Bart, Kyros) or watching quietly (Law). It's as if there's a complete reversal of what I tend to expect from One Piece in this climax. The less colorful, less built-up characters are at the center stage of attention and tension in the very climax. Meanwhile the great, classically One Piece, emotionally engaging characters (which the arc has plenty of) are relegated almost exclusively to serving Oda's favorite plot device or doing what seems to be nothing at all.
And worst of all, the citizens of Dress Rosa. They are a giant faceless mass that have been bumbling around and running from Bird Cage forever. I can't get emotionally connected to a mass of faceless people just because what happens to them is sad. It doesn't matter how many panels of them looking sad or scared or overjoyed Oda hits me with (I think around 10-12 in this chapter alone?). It won't happen =/ The emotional connection I get to One Piece characters is through getting to know them and spend time with them, learn about their personalities, their history, and follow them through their personal struggles. It can be both on the small and large scale: Senõr Pink or Nico Robin. But it won't happen through simply being told "sad thing happened, now feel sad" and showing more and more panels of sad things happening to people that remain as faceless as before. The citizens of Dress Rosa being made such a huge emotional anchor was a massive mistake to me.
The next chapter is probably the one that will work, because it'll contain Law's reaction. He's the character that's both colorful and interesting and had a great deal of attention and love devoted to writing his emotionally engaging story full of characters just as colorful and interesting. But this one just couldn't do it for me. It's not because anything about it was wrong per se. It's natural to have exactly this happen as Doflamingo is defeated. It makes sense in-universe. It's what logically follows the story as written. But the characters focused on simply are not engaging. Without engaging characters, a character-driven story just isn't much to write home about. They exist in this arc, but they aren't these characters.
A lot of this chapter will depend on personal opinions. Like you and some others, you don't care for the citizens or King Riku, and Gatz is a bit of a miss. Therefore, this chapter is quite weak because it didn't focus on the characters you wanted it to.
As far as the Gladiators, I don't think they needed to have focus on this particular chapter. This was about the country itself, and their stake in it. Some of the Gladiators had come for a certain purpose, but the country as a whole didn't matter to them.
While it won't make a difference, I feel there was a little more to the masses than you give them credit for. One thing that stuck with me was how many of the citizens became toys, and were forgotten. I still remember the scene where the toy dog tries to convince his child and wife, and is thrown away. It showed the darker side of the country, and how many citizens were being harmed without anyone knowing. You had the soldiers being forced to fight, and seeing them all injured but forced to continue fighting. I remember that along with the birdcage stuff and it makes it more effective to me.