I think the mistake you are making is in viewing everything through the prism of carrier strike group operations.
Yes, CSGs are tip of the spear, best of the best door kickers, but your whole war machine can’t just be about the speartip.
The CSG, 055s and 052Ds are the sword, the 054A/B and 056s are the shields.
As the CSG engages enemy core fleet elements and eliminate them and shatters the island chains to push further out into the open pacific for offensive combat operations, that leaves ever increasing amounts of deep rear real estate to patrol and guard. And it’s not like the PLAN is going to make a beeline for Pearl or San Diego as soon as it’s punched through the second island chain. Most likely, they will seek to establish a cordon in the mid pacific and defence that against enemy forces seeking to breach. That’s what the 054As and Bs are for.
These ships are not meant to face off against enemy fleets or air wings directly. They are there to catch leakers that slip past the CSGs; provide survivable (against the threats they are realistically expected to face) patrol and sensor coverage to ensure there are no or at least minimal sensor dead zones around and behind the CSGs; and provide early warning and first response against any enemies forces that seeks to slip past or flank friendly CSGs.
For that kind of mission, endurance is the primary requirement, speed is secondary.
Sure, having just as many 055s would be far superior, but even China has budgetary and resource limits and cannot build 055s like they are 054Bs.
In that respects, the 054B holds true to the PLA’s core tradition that good enough is good enough. That’s how they have the budget left over for all the no-expense-spared top tier goodies without drowning China in debt like America has done trying to get gold plated everything.
