Even then, I don’t remember the actual Rebel Alliance having any major victory during the events of Star Wars Rebels. All of the main victories are attributed to the smaller cells (such as Phoenix squadron) on their own.
The first large military action of the Rebel Alliance was meant to be the Liberation of Lothal, but the plan was aborted as the Alliance debuted with a hard defeat at the hands of Thrawn. And when they eventually succeed in liberating Lothal, it wasn’t thanks to the combined strength of the Rebel Alliance, but rather to the main characters assembling a ragtag group of allies as the Alliance couldn’t afford a full-scale assault, especially as the one time the Alliance directly intervened by sending a X-wing squad to Lothal, they were utterly defeated.
I agree the battles depicted in Rebels could have strayed a little more off the OT customs, but then, the entire show since its inception was sort of a love letter to the Rebellion era.