I think it should be interpreted that way because it is now obvious that Oda never had any intention of lifting Roger above others.
At least not when it comes to individual strength.
Yes, the new gen in 20 years is about the prophecy but you forget that Oden knows the strength of Roger and Whitebeard first hand, he fought both of them, he is very much aware that if he fails, nobody else is strong enough to kill Kaido either.
And then you add in the context of Oden returning many times stronger and called by author invicnible and triumphant as well as author saying that might of Kozuki Oden surpassed Kaido's expectations while treating him as mighty pirate like Roger and WB, as well as Oden's own statement that his sword style is the best there is and the fact that Oda chose only him to leave a scar on Kaido...
...there is only one logical conclusion to this - Kaido>Oden>rest of the old generation.
"you forget that Oden knows the strength of Roger and Whitebeard first hand" I didn't forget, I made this argument countless times. You just agreed the prophecy is about the new gen being the one to do it. This still doesn't prove this
MUST MEAN Oden thinks Roger and WB won't do it,
because they are weaker than he is. All you have done is spoken for the character. You can't prove this objectively.
"And then you add in the context of Oden returning many times stronger and called by author invicnible and triumphant " - I understand this as well. Over the voyage he got stronger. Surpassing Kaido's expectations and Kaido giving him respect, these things aren't clear indicators that Oden has surpassed Roger and WB. In fact you saying "like Roger and WB" isn't "More than Roger and WB". This doesn't show Oden is > Roger and WB either
Odens swordsmanship being stronger is a self proclamation, not a confirmation.
You use language like "I'm telling you what the author said" or "the narration confirms this", but your stance does not come from objective facts. My reply was to show you your interpretation is not an objective one. I used to have your interpretation, until I realised in the context of a prophecy it does not
Have to mean anyone in Oden's time is incapable, only that they aren't the prophesised to do it, Joyboy is.
And this is obviously heavily tied to the narrative, it's common sense this is the explanation for why Kaido wasn't taken down before Luffy got to him.
Coming back to Oden's proclamation,
even if for the sake of argument I give you that Oden's swordsmanship is stronger. It doesn't guarantee Oden is stronger than Roger. All this would mean, is that if Roger learnt Oden's swordsmanship he'd have the potential to be more lethal. But you can still use a weaker sword style than someone and be stronger than them.
Look at Shanks, I think Shanks is not only stronger than Roger using his own swordsmanship, but is stronger than Oden, using Rogers swordsmanship. Which according to you must be inferior because Oden said so whilst knowing Roger. To me this just shows Oden's supreme confidence in his own abilities.
"the fact that Oda chose only him to leave a scar on Kaido..."- This is not a good argument. This makes sense from a narrative standpoint considering it's Oden's homeland being affected, and he is the daimyo. To Oden this was a kozuki matter, he wasn't going to accept help. Ofc he would be the one to scar Kaido in a direct confrontation where Kaido is the tyrant in his homeland.
The thing is you're using who leaves a scar on Kaido to be the prime indicator for portrayal. But when was Kaido stated to be this kind of objective marker? Just because a character scars Kaido defending his homeland, doesn't mean he must be stronger than a person who has not, especially when there is no direct comparison.
For example you can say he's stronger than Moria, because moria came back to do the same thing Oden did, and he failed to scar Kaido. Yet Roger or WB was narratively kept out of Wano's borders for a reason.
Roger even went out his way to avoid BM and simply stole her glyph, he didn't have to scar BM for example, he wasn't defending a country against her tyranny. Are we going to say Law and Kidd have better portrayal simply because they took her down when Roger didn't?
In fact Kaido is wanking Roger without Roger having ever scarred him in the narrative.
The point that doesn't seem to be getting across is, this prophecy on Oden's part cannot objectively be used as a method of scaling him about Roger and WB, when the prophecy never claims anyone outside of it is too weak, only that they are not the chosen ones to do it.