Reshiram and Zekrom honestly don't seem all that different from Zacian and Zamazenta, with the only major difference being that Zacian and Zamazenta get along. Actually, they're arguably lesser than Zacian and Zamazenta. Zacian and Zamazenta may or may not have fought Eternatus on their own during the first Darkest Day, while Reshiram and Zekrom explicitly served two heroes back in the day and put themselves in a dormant state so they could once again serve heroes in the future.Groudon and Kyogre make the land and sea their domain, Dialga and Palkia control the fabric of reality, Reshiram and Zekrom are the embodiment of truth and ideals, Xerneas and Yveltal govern life and death, so on and so forth. I don't believe these concepts are bad in-and-of themselves, but being unique deities that lord over these powers is.
They're not the embodiments of anything. They're just politically aligned.