I don't rank Whitaker as highly as most. If I ever took the time to make a list of the guys I consider the top 100 p4p fighters, he wouldn't be on it, but then neither would Ali.
As a LW he isn't beating Duran, Benny Leonard, Armstrong, Ike Williams, Gans. I don't see him beating Beau Jack or Bob Montgomery, after talking to people that saw them (and Whitaker) fight from ringside. I don't think he beats Lou Ambers, who gave Armstrong such hard fights. I don't think he beats Carlos Ortiz and I don't think he beats Ismael Laguna.
At WW, he doesn't do well with the champions of the division. Even the overlooked guys like Zivic beat him; he fought Robinson tooth and nail twice, beat LaMotta and lost 3 or 4 split decisions to him. Guys like Tommy Bell beat him, and he was never champ, same with Charlie Burley.
At LW he might make my top 20, if I ever made a list. Not my top 50 at WW. Too many really good fighters and Whitaker's shuck and jive nonsense wouldn't impress them and, offensively, he didn't have enough to hang with the guys that would fight through his games.