Would the enemy care about China's equivalent? Why would the PLAN not build something equivalent to the LCU 1700 especially when it has the means? It's not a DDG costing hundreds of millions.
Because a larger LCU like LCU1700 is too big to allow maximal carriage inside the welldeck of 075 and 071, and the PLAN doesn't need a separate larger LCU like LCU1700 because it already has other ships for that weight class and role.
The new PLAN LCU is small enough to allow side by side carriage, as we can see:
In terms of dimensions, it means they can fit two of the new LCU in the space of one LCAC. So for a 071 or 075, it means you can carry twice the number of LCUs as you can for LCACs. E.g. for 071 that means up to
eight of the new PLAN LCU.
That is similar to the French EDA-S where they can fit two EDA-S in the space of one EDA-R (which is similar to a LCAC in size) in a LPD or LHD:
The USN's MSV-L is similar, as it is designed to replace the legacy LCMs they have in the same footprint, which can fit two alongside in a welldeck of a LHD or LPD:
Compare that to the LCU1610 family (which is similar in size to the new LCU1700 that is replacing it).... note that it is too big for you to fit two LCU 1610/1700 sized ships in the space of one LCAC:
.... For larger conventional landing craft, they have something different to the LCU1700 family -- they have the Type 271III LCT family, which is a bit larger, able to carry two or three MBTs in a covered environment, and is not designed for carriage within a 071 or 075's well deck (because it doesn't need to be).
... so to go back to your question -- "why doesn't the PLAN build an equivalent to LCU 1700 class?"
The answer is: the PLAN doesn't need an equivalent to LCU 1700 because it already has landing craft of other sizes that fills the role, and because this new LCU is deliberately designed to be more compact to allow maximal efficient carriage inside a welldeck which a larger LCU like LCU1700 cannot do.
My counter question to you is: "why do you think the PLAN should build an equivalent to LCU 1700 class to begin with"?
Because you seem to be thinking that simply having a larger payload is better -- but you don't realize that the LCU1700 is a bigger ship than something like the MSV-L, EDA-S and the new PLAN LCU, and it means that they won't be able to efficiently fit them inside the welldeck of a 071 or 075, meaning you will end up wasting welldeck space.
In that case, why is a LCU 1700 class ship necessary?
After all the PLAN already has LCTs like the Type 271III which is similar in size and optimized for regional shore to shore missions (i.e.: not intended to be used for welldecks).
