@Admiral Lee Hung thanks for the new chapter! This is current day Shishi to the spot.
YouTube guy's faces nearly killed me. The arm was an incredible touch ahaha. And I love the horse. He's always there with mute support.
Considering that we can get wildly differing opinions on opposite sides of the spectrum regarding the quality of Katakuri’s character then perhaps it is fair to say that Katakuri is a good character with a compelling thematic concept that was executed poorly?
I remember at the time, the three things that turned me off Katakuri were;
I) His presence completely undermined Linlin’s status as the arc antagonist.
An antagonistic character should be someone that opposes the protagonist in a meaningful way, usually through opposing or differing morals, ideologies, outlooks on life, principles etc. etc.
Katakuri clearly had a far more developed role as an antagonist than Linlin which is honestly astonishing since Linlin is a major series antagonist that was revealed all the way back in Water 7 as one of the greatest pirates of the current era and to have ever lived.
In comparison, Katakuri was practically introduced at the last possible moment, being introduced during the beginning of WCI Arc’s climax. For him to outshine Linlin is completely unprecedented and would be akin to Mr 7 and Miss Father’s Day outshining Crocodile.
It is not like Linlin had no opposing ideology to Luffy either. For starters, their views on family and loyalty are chalk and cheese. Lol.
I know one could say that Linlin could shine later in the story (fat chance, pun intended) but it is the first impression that is always the strongest when it comes to story telling and Linlin’s first impression was completely undermined by Katakuri.
II) The reasons for the fight to occur in the first place were nonsense and undermined Luffy’s previously established character.
Luffy was never someone who started conflict with any major arc antagonist. It was always an antagonist that started shit and blocked all options off to the point where Luffy had to confront them for a logical reason (e.g. Crocodile and Alabasta, Enel putting the SH crew on trial, Moriah trapping the crew, CP9 capturing Robin etc.).
Luffy was always more concerned with the safety of his crew and adventure. Deliberately picking fights for no reason was not in his nature. Just look at his interactions with Bellamy during Jaya Arc. Luffy had no interest in an ego contest with Bellamy because such things are meaningless, a lesson he learned from Shanks all the way back in Chapter 1.
Compare that to Luffy abandoning his crew (which is down to 1/2 it’s usual numbers) to a literal Yonko in order to have a fight with Katakuri for the sake of fighting and it suddenly feels less like Luffy vs Katakuri in One Piece and more like Rubber Goku vs Demon King Katakuri in Dragon Ball Sea.
The old Luffy would have prioritised the safety of his crew above all else. Luffy has the chance to either trap Katakuri in the Mirror World by dumping him in there and taking Brûlée hostage or just straight up dumped Katakuri in the ocean. Then he would have protected his crew from the rampaging Yonko Linlin.
Before I hear some objections about how Luffy is not “underhanded”, this is the same Luffy who regularly used people as meat shields since Pre-TS and who was fine with partaking in the assassination of a 68 year old granny by directly triggering a catastrophic mental breakdown.
Seeing such a core aspect of Luffy swept aside just to have a cool fight was utterly disappointing.
III) The entire fight happened during the worst portion of WCI Arc, if not the worst portion of the entire manga. To this day, I am still of the opinion that WCI should have just ended after the Tea Party finished.
I think your approach to all of this is a bit off, I will make it short.
I) Katakuri is the true arc antagonist, because Oda needed Luffy's power up without Linlin losing face. Clearly his goal was to show how far he is from facing a Yonko. But as he had to make a final battle for Luffy, Katakuri is a brilliantly executed replacement. It helps that he's an interesting character. Linlin's impression was not diminished because she is portrayed as pretty damn invincible. Don't project your potential personal opinion of her when clearly she's done nothing but rampage and scare everyone.
II) It didn't diminish Luffy's character at all. He picked all his major fights so far (bar Kuma? But that is not really a fight per se). He even accepted Kaido in a heartbeat without a single reason after Law suggested it. He threatened Big Mom and Doffy over the
phone den den mushi. You say he did for a logical reason, but the fact remains that he did pick them. That is literally his trademark at this point, picking fights around the world. Did he even know
why he picked a fight with Arlong? No, he just went for it because Nami was hurt. He does it all based on a whim or feeling.
Post skip Luffy is more focused on gaining power. Kuma and Ace were the lessons which taught him that he must become stronger. He didn't initially want to fight Kata, but he was cornered and he saw a challenge.
The fact that he saw an opportunity to learn from overcoming Kata was incredible character growth for Luffy, not undermining. Please don't put him in a box, it's enough that we have a simple minded MC, but it's not true that he can't change because we already saw he did in many instances.
When they clashed it was easy to see how Hawkins can counter Law, but Law did manage to get rid of his fodder. Hawkins came out on top though, because later he managed to capture Law, proving he was smarter. Law only ''defeated'' Hawkins, because of the unknown person that freed Law. 
