To me, yes, but mostly to avoid retconning Leia’s character. Instead, her becoming queen in ROTJ (as suggested by Kurtz) and proving worthy of the title protecting her people against the Empire, would’ve made for a better character development and a better end to her narrative arc.
I think the whole queen crap is ridiculous. It would make the rebellion stupid. They were fighting to get rid of dictatorship, not to go from empire to monarchy. And btw, “her people” were all blown up in ANH.
The way it is now makes for a far better character development. We first meet her as a spoiled royalty in ANH. By the time of ESB she seemed to have become respected by the rebels because of her skill rather than the fact that she was once a princess. In ESB she even hates it when Han calls her princess, which implicates she put that stuff behind her and that she is not proud of it. The old EU actually made the final transformation, i.e. into a politician in republic/democracy which is a direct opposite of her status at the beginning of ANH.
I think the Amidalas being monarchs doesn’t necessarily mean the people of Alderaan are/were under dictatorship: maybe it’s like a modern democratic monarchy like the UK (which is member of the EU, a democratic union of states kind of like the Republic), so there’s no contradiction here.
About the “her people” issue, I don’t think it was confirmed in the movies that there weren’t survivors, away from their home planet.
But in any case, my point is that to me Leia becoming a queen or leading the Rebellion would’ve fitted her character more, being Leia a princess taking more and more responsabilities in the war (stealing/keeping safe the plans, helping on Yavin IV, co-directing the battle of Hoth). I don’t think she was spoiled in ANH, quite the contrary. Very cold and young, sure, yet a loyal leader.