There are two things to consider here. Firstly just because we don't get pictures does not necessarily mean assets are not in place.
LCACs, by nature, are highly offensive oriented assets, given recent tensions in the SCS, it would be totally understandable if Beijing opted to purposely suppress LCAC deployment news to avoid alarming the neighbours.
But if we assume, for the time being, that the lack of visible progress does indeed mean a lack of new LCAC orders, then that would indicate one or both of the following factors apply.
1) what are the PLAN's primary potential amphibious assault theatres? Taiwan and the SCS.
China lacks the logistical bases and the need to launch large scale amphibious assaults further field.
Without foreign local bases, launch an amphibious invasion is pretty much impossible from sea base assets only unless we are talking about small islands like the Falklands that could be isolated and cut off from enemy reinforcements.
But even then such an operational would be massively risky, and almost certainly costly. Far more so than would be justifiable for any Chinese overseas assets.
Any long range amphibious operations the PLA is remotely likely to undertake outside of Asia would thus not involve the kind of head-on heavy beach assaults you would need MBTs for, and would be largely limited to humanitarian rescue and relief operations; evacuation of Chinese nationals from war torn regions and maybe some small scale special forces ops.
For those kinds of ops, the PLAN are far better off with packing more of their amphibious IFVs onboard 071s rather than sacrifice dozens of IFVs to carrier a handful of MBTs.
Within Asia, we also need to take into account just how much of a game changer China's new built island bases in the SCS are.
From them, Zubrs have range to reach any potential target zone in the SCS with far more, and heavier MBTs, removing one of the primary rationales for 726s on 071s.
2) Speaking of MBTs, has anyone seen pictures of 726s carrying anything heavier than an 96? The 96 in question was also stripped down, without its usual ERA modules IIRC. That would suggest it currently lacks the payload to carry out its core intended mission to me, which may be why the PLAN is holding off an ordering more until a version able to carry the 99 and new 99A2s become available.
I think this combination of having a better delivery option for MBTs and other assets within Asia; a lack of a desire or need to seriously consider large scale offensive beach assaults further afield; together with potential performance shortcomings in the 726 would explain why the PLAN might be holding off on buying more.
I think the PLAN will likely put much greater emphasis on LHDs compared to LPDs in the future, as airborne assault would be far more suitable for the kinds of operations they might realistically be called to perform far from home.
LCACs would will be an useful capability to have, so I am by no means suggesting the PLAN will ditch them.
My main point is that there is no real pressing need for China to acquire LCAC capabilities on a large scale at present or in the near future. As such, they can afford to take their time and be a lot more demanding if the level of performance they want from their LCAC before commiting to a large order.