Even in theory he is wrong. In order to even go after one piece aka reach raftel something only Roger has done out of all the pirates till now.. You'd clearly have to be near his level. And going to Raftel, would also mean messing with the Yonko, who would be threatened by you becoming PK, so you will face them automatically. And if you happen to run into a yonko, on one of the islands that you have to stay on for the log pose.. then what would you do?
And Yonko aren't the only enemy in trying to reach Raftel, you also have the admirals who will try to stop you from reaching Raftel since it will trigger the biggest war of them all. So you will need to be stronger than them as well.
Riker and Vandriech like to use Buggy (someone who doesn't stand a chance against any of the Yonko Armies or against any of the Admirals and their armies), as an example. But what they fail to realize is, gaining fame and building a strong military as a weakling, and that leading you to become a warlord, is different from becoming the PK.
And on top of all that, we still don't know the big reason, why people haven't been able to reach Raftel except for Roger.