I don't think anyone would claim the Burke III's propulsion is cutting edge but for this day and age I think you would be hard pressed to say they cannot still be considered reasonably modern.
The point is that we have not yet reached a point in naval propulsion internationally, where we can have the gall to call anything other than IEPS or COGLAG as "subpar," simply because there aren't that many surface combatants out there with IEPS and COGLAG or equivalents to begin with. In many respects the European navies are on the leading edge in this regard, but the point still remains that this kind of propulsion technology is far from the norm for international navies.
Thus, I reiterate my previous point, that I see nothing wrong or "subpar" if 055 uses COGAG propulsion, especially if it is only the first batch.
The basic Burke-class is like 30 years old. Even if AEGIS and the amount of VLS cells are still stunning characteristics so are several features not state of the art anymore.
Also looking at other ships in that size classes. The new batch of Burke-class ships are the only one we know will use the COGAG system. All other navies moved over to diesel-electric or even full electric propulsion - the US Navy was also planning to move to IEP and the Zumwalt-class (and the cruiser-version) as well.