Luffy is cool.
Nika is just not for me lol
I will argue that Gear 5 in Wano was great, and not the problem with the arc at all. Wano's Samurai were so focused on revenge and anger and failure, that they couldn't succeed.
Luffy shrugging off all of that revenge, anger, and failure to defeat a man absolutely destroyed by those feelings (hell, the little bit of God Valley we have shows Kaido wanting to pick a fight with Roger over a grudge), by just laughing in his face, is so poetic. Kaido's strength of spirit was never the problem. His hatred was. This is shown through Yamato. Kaido talked about how humans would treat Yamato horribly, but, we've seen so many instances of humans loving Yamato. Kaido was the one who hurt Yamato, not humans.
Wano Gear 5 was Luffy nearly dying, then coming back to life through a miserable people's wishes, and using laughter to defeat a depressed monster. I understand why people don't like it, but, Oda clearly put thought into it and tried to make it work well.
Egghead Gear 5 is just Luffy doing whatever he wants at the cost of the plot and tension at times. The fact that his only cooldown is needing eat to meat is bad because it's so predictable. Oh, G5 is out? Feed Luffy. Rinse and repeat. Luffy's moments with Bonney are actually really cute and wholesome, but everything else outside the Lucci fight has been hit or miss for me.
I can totally understand why people don't like Gear 5, it makes the plot less serious, and Egghead has had issues with that.