First of all I think @Sadistic Senpai gave a perfect explanation as to why it is still speculation and why Kanjuro is a prime candidate. The points you made are worth discussing, but they could also easily be solved by Oda as of right now.
Who is your candidate btw?
Jack didn't just think that Raizou might be on Zou. He knew Raizou was on Zou, which is knowledge Kanjuro never had and was only available to the minks who witnessed him arrive.
Not only that, by the time of Raizou crash landing at Zou, Kanjuro was already fully aware of the meaning of the crescent moon ankle mark. He knew that it was a symbol of the rebellion since he'd been told that from before they even left Wano. So why did Kanjuro hold knowledge of exactly who the rebels were in Wano if he was the traitor? Why would he not inform Orochi so they can round them up? Not only that, but throughout the entire time Luffy and co were on WCI, Kanjuro was undercover on Wano with the alliance. He knew what everyone was doing. He knew Robin was training to infiltrate Orochi's castle. He knew Zoro and Usopp were recruiting. Yet no information or anything got leaked in this time. The leaks started happening shortly after all of this information that Kanjuro had already long known, started to get revealed to the WCI group.
So Kanjuro reported to Kaido the location where there was a chance Raizou could be, but didn't mention anything about the rebel symbol at Wano for weeks, despite knowing about that before the Raizou situation?
Because other characters that are often discussed (Carrot, Shinobu, Law) have a million times more arguments against them being the traitor, than Kanjuro does.
-What about the countless panels of him crying alongside the other scabbards and speech of what must be done, totally in sync with the rest of them.
-What about him rallying Luffy to join them and fight?
-What about the prophecy of 9 ghosts killing Orochi?
-What about the fact that Kanjuro has known the other scabbards since he was a kid and has guarded Momo?
-What about the inconsistency of the timeline of leaked info?
-What about Kanjuro rushing to Oden castle as it burned down to protect the Kozukis?
I think the traitor is Kanjuro, but there is a lot doesn't make sense, so I'm doubtful Oda can justify things upon the reveal.