I completely agree with you. In fact I prefer it in the case of something like Guardians.Which can be good or bad. In a movie like Thor where the main characters are safely established, the lack of a compelling antagonist in the sequel was a big letdown.
In a movie like Guardians where Gunn has to split his focus between introducing so many cosmic elements to the MCU, introducing all these characters and villains, and bringing them together as a team worth rooting for, I don't mind if the villains take a backseat.
I just hope Ronan isn't the caricature he seems to be from the trailers and that they don't just kill him off and neuter future development. He deserves a lot more than that.
TBH I'm still not on board with Ronan completely. I don't really like his look, it lacks the nobility and he just looks one dimensionally evil. I'm more used to him in the comics recently though, reading up on wiki it seems like he was initially introduced with that sort of temperament. Perhaps there are more political overtones in the film though.