It was mostly because that's just something people liked to say for older candidates, even though it didn't really make any sense. It was always vague statements like "This is what Oda always does and it'll be no different this time" and "Even if they're too strong, they won't be so strong that the Monster Trio can't surpass them in this arc". The latter isn't always incorrect, but in this case, both just don't work with Loki.
With regards to the M3, we've already had several conversations on this topic before.
Zoro and/or Sanji > new additions isn't always so clear cut. Examples of such cases being Robin & Jinbe when they joined.
The only ting that is certain is that they will eventually establish superiority over any new addttion. Now the argument is going to be that Loki is way to strong for them to make up that gap which brings me to my next argument which is the bit you quoted me on.
"Oda will eat his cake and have it with Loki, this is what Oda always does" is in reference to the inconsistencies in Oda's writing paticulary with regards to PLs in one piece. Oda doesn't care about logical consistency and will write whatever the fck in order to get your attention and then contradict or bin that shit the next minute without batting an eyelid.
There was a lot of examples of this on Wano.
Kaido's world's strongest title, which isn't looking so hot just one arc after so much so that Kaido > Shanks is looking hella sus atm.
The Supernova gas and hype which he quite literally wiped his ass with and binned just one arc after.
Zoro's rooftop performance with him slicing up Kaido right left center, blocking Hakai only to be then get rag dolled by King and paired up with Sanji as the wings of the PK and then struggle with Lucci till Sanji put a rod up his ass.
And this is not just only with PLs he does this with fake deaths as well. Kiku's supposed death tease on Wano was a very good example of this (mofo then killed Ashuradoji and Izo in the shittest way ever just coz he wanted to kill them off). Could go on and on and on. Right now the focus is on Loki and his DF and Oda's gassing it up to high heavens to get our attention but don't be surprised if he dails that shit back after he's had his fill with it and wants to gas up whatever he wants to gas up next. Wings are going to get their hype soon, Nika will also get his and even Shanks who suppossedly captured Loki.
Which is why I'm uncovinced by the argument that Loki is too strong to join. If this were Jujustu Kaisen or H x H then fair enuff but this is One Piece. As good a writer Oda is, he can be very lazy and shameless with his writing.
Anyways that's were I'm at with the whole Loki ting. We can of course disagree on this.
Anyway, the god of war isn't revered as much as Nika is, because Nika is a liberator, and the god of war isn't. Therefore, the god of war is less popular.
Despite that, the god of war wasn't said to have lost to Nika/Joyboy in their clash, and the Nidhogg fruit is also explicitly shown to be the antithesis to the Nika fruit in almost every way.
Luffy is white, Loki is black.
Luffy brings the dawn, Loki brings the dusk.
Luffy is constantly laughing and has a cartoonish, friendly look to him while Loki is dead serious and looks extremely menacing and cold.
And now both of them are heading towards Imu to fight him at the same time, similar to Law and Luffy going to fight Doffy or Law and Kidd going to fight Big Mom.
Loki is portrayed as the yang to Luffy's yin. He won't just be his subordinate as that misses the entire point.
This isn't to say it's BAD to be a subordinate of Luffy, but Loki specifically is not portrayed that way. He's not the Vivi of the arc, he's the Law of the arc.
With regards to Luffy/Loki comparisons I think you're jumping the gun a bit and it's a bit too early to make such assumptions but I digress we'll see as the arc transpires.