I think they were more reluctant of having classes that were available to all races back then. Out of the 3 classes that are available to all races now (hunter, warrior and DK) only warrior was available to all back then. Hunter was not available to gnomes and DK was not available to pandaren (partially probably because they’d have to be retconned into the DK starting experience). Pandaren monk trainers were also retconned into starting zones in MoP, but as Gilneas and Kezan were more isolationists, worgen and goblins were not given monks.
Anyway I believe that worgen and goblins do have monk animations. Whether those were there from the start or made later I don’t know.