Let's face it - when it came to movie musicals - few studios could hold a candle to MGM.
WB made some musicals before DD-------Yankee Doodle Dandy, Hollywood Canteen---spring to mind but the bulk of the truly great ones came from MGM. 20 th Century Fox was fortunate to have Betty Grable, Alice Faye, Carmen Miranda and others that lent excellence to those musicals much as Doris was to do for WB.
MGM seemed to have the budgets to produce spectacular results plus better production teams so that their musicals were unparalled in movie history and their list of titles that became classics is indeed staggering.
WB could never match that record. WB was primarily a studio capable of turning out great dramas and for many years ---- those gritty 'film noirs' became their stock in trade.
Then Doris came along so then WB had to jump on the musical bandwagon. True she brought everything to these films but she did get to work with some fine people there--both onscreen and off-----and she was able to polish and hone her craft so when she finally moved on from WB------she was able to segue into far more substantial projects----LOVE ME OR LEAVE ME, MAN WHO KNEW TOO MUCH where she finally worked with a 'biggie' director in Hitchcock so WB was for her ACTING 101-----'On The Job Training' and therefore a means to an end.
Yet the WB years were not without their highlights in her career.
In fact her very favorite role - CALAMITY JANE - was from WB and this was the film she truly likes the best of all the ones she did.
So at least WB did a few things 'right' in her case !