No doubt In my mind that Mizerak, like Sigel and Varner, got far fewer votes because of how few who voted saw Him at his peak level.
I think you are probably right. It is same here in UK many people under the age of 45 never saw Steve Davis is his prime between 1980-1990 and therefore class him below certain players playing today.
Having watched every snooker player for past 40 years i would still have peak Steve Davis in my top 5 , especially when you consider the playing conditions back then compared to super slick napless cloths of today.