Because Foreman is a clueless slugger Wilder can only throw a right hand and has terrible balance and coordination and almost zero ring iq yet he becomes world champion so that shows the state of the heavyweight division right now. Ali didn't headlock Liston all day he showed amazing boxing skills and quick feet and made him miss most of his shots with his elite head movement. Usyk would be one of Ali's toughest fights of course. Only a blind nostalgic fanboy would say otherwise but if you're writing off Ali's achievements and his skills you just must be a blind modern fanboy
It could have been either a very exciting fight.. Or a very boring one. Usyk would be too slick and too agile and cat like for Ali I think. (Just an opinion) Boxing has changed so much.