Whitebeard was known as the closest to one piece, who ruled the seas
So likely that because of his power, the silver medalists couldn't go everywehre they wanted, let alone finding the last poneglyph/reach Laugh Tale
WB has mentioned to be the lynchpin in the stalemate. Basically the other three yonkous are equal while WB is sitting above and hindering risky movements through his sheer existence.
Answering to both.
I'm not saying it was impossible, I'm just saying I'm not convinced yet. I have no problem with Primebeard > Yonko (Oldbeard is another story), but if he's not interested in blocking anyone, his power level doesn't matter... To me a clear example of this would have been WB having the fourth Poneglyphs. Saying I don't care about going to Raftel + keeping the fourth Poneglyphs = Yeah, I'm not letting Meme, Kaido etc. go there either.
But 1) the 4th stone is hidden. So even if WB has it, it's a secret. There was never a direct challenge to Meme and the others "come and get it if you want". 2) WB never cared about Roger going there, he did not block him. I don't see any indication that WB would
directly block other people from going. 3) We have seen in the last few years how the idea of the Yonko constantly fighting each other was a farce. These guys don't see each other for decades....... Unless the 4tn stone is hidden somewhere inside WB'S territory I don't see how WB was blocking anyone. For now, Meme and Kaido were much more of a block, keeping one stone each.
The only indication at the moment was that he was waiting for Ace to reach the top. But to me WB seems a guy that would "nurture" Ace and then, when the time is ripe, would tell him "Ok, if you care about it then show me what you have got and go get it for yourself".
EDIT: Now that I think about it... WB didn't even help Wano... And you think he was stopping people from going to Raftel? Nah.