Luffy and Law are not rivals. Law couldn't even handle Doflamingo. Just because you're a fan of his doesn't mean he needs to be even remotely close to Luffy. He's nowhere near as strong and doesn't need to be either. He's Luffy's friend now.
Lmao I don’t know where to start. Luffy and Law are not rivals, despite being portrayed to be, again, within the last ten chapters, because they’re
friends. Somebody had better let Roger and Garp know that they weren’t rivals, on account of them being friends. Same with Whitebeard and Roger. They weren’t rivals because they were friends. Despite, of course, being stated to have been rivals, but you know, head canon comes first.
“Law couldn’t even handle Doflamingo” despite that he fought the entire day against Doflamigo in 2v1 scenarios, first against him and Fujitora and then against him and Trebol, and despite him putting Doflamingo down but for an emergency surgery ability that only Doflamigo possesses. Oh, and also despite his mental/emotional state, which had been stated and shown a few times in the story to be impactful if negative.
Marco would absolutely take a shit on Law. Katakuri was doing it to Luffy and Luffy had beaten an actual commander before this. If you think Law evens stacks up somewhat well against the likes of Marco or Luffy, then I really don't know what to tell you...
Law is going to fight alongside Luffy against Kaido, but you think he wouldn’t be able to handle a commander nor that he would stack up against Luffy or Marco. Solid logic.. Keep that logic with Zoro if you ever argue him going against a commander in this arc, having never fought one.
And Marco isn't a main character. He's gonna do cool stuff in the arc and be a big player but the fact is Zoro is more important as he's an actual main character and will get more individual focus than him. If you think Marco will shine more than Zoro this arc, then you're either biased against Zoro or biased towards Marco.
This is all kinds of nonsense, given literally two of the last three arcs, when Jinbe got more focus than any Straw Hat barring Luffy on Fishman Island and Law got more focus than any Straw Hat barring Luffy on Dressrosa. Hell, you can argue that Law has as much focus as Zoro does in
Wano, which fanboys proclaim to be Zoro’s arc. Marco will absolutely be getting a ton of focus, especially as we draw nearer to Teach, and probably more so than any Straw Hat barring Luffy when it’s time.