There is most likely a trick to getting to Raftel as many have already stated
As to why none of the Yonko have found it yet is hard to say, all of them would have territiories in the grand line that they would have to protect this would take up some time that could have been spent sailing towards Raftel
We dont know enough about Big Mam or Kaido to make any assumptions as to what their motives are or how close they are to finding One Piece, that being if they are even interested in obtaining it.
Whitebeard as we already know was the closest to finding One Piece but he didnt want it he just wanted to have a family more than anything
Blackbeard obviously wants it but i think at the moment he is more focused on his aquiring of power, plus we still dont know if they have replaced their almost destroyed raft they had been sailing on i doubt that thing could had made it all the way to Raftel. (I assume that they have though after the time skip)
Finally
Shanks is quite laid back taking his time travelling and most likely spends long periods of time in places he likes such as when he stops in at Luffy's hometown and they end up staying for like a year or something. I think though that Shanks even though he probably knows how to get to Raftel being the former cabin boy of Gol.D.Rogers crew he doesnt want it as he knows that Luffy will be the one to find One Piece and become King of the Pirates
As to why none of the Yonko have found it yet is hard to say, all of them would have territiories in the grand line that they would have to protect this would take up some time that could have been spent sailing towards Raftel
We dont know enough about Big Mam or Kaido to make any assumptions as to what their motives are or how close they are to finding One Piece, that being if they are even interested in obtaining it.
Whitebeard as we already know was the closest to finding One Piece but he didnt want it he just wanted to have a family more than anything
Blackbeard obviously wants it but i think at the moment he is more focused on his aquiring of power, plus we still dont know if they have replaced their almost destroyed raft they had been sailing on i doubt that thing could had made it all the way to Raftel. (I assume that they have though after the time skip)
Finally
Shanks is quite laid back taking his time travelling and most likely spends long periods of time in places he likes such as when he stops in at Luffy's hometown and they end up staying for like a year or something. I think though that Shanks even though he probably knows how to get to Raftel being the former cabin boy of Gol.D.Rogers crew he doesnt want it as he knows that Luffy will be the one to find One Piece and become King of the Pirates