Depending on the continuity, Diana gains her powers from an external magical source (the goddesses) that effectively isn't that different from Clark's biology + yellow sun power up. And Amazon training which was designed by Marston to give them superhuman strength and stereotypical "Venus proportions" to explain why they were also conventionally attractive.
Wouldn't have any issue with Diana having a Ronda Rousy body type, but nobody wants to look at a Superman that resembles that picture of David Schwimmer