I don't think the PLA not developing a common rail system has anything to do with technology or mentality being 'stuck'.
The decision is based on pragmatism and prioritisation.
Sure, having a rail and all the newest gadgets is cool, but even in the US military, the majority of accessories are simply not used. Sure they could be useful, but the very limited chance of that particular situation coming up is offset by the weight penalty of having to lug that thing around with you all the time.
Adding a common rail is pretty basic and easy. The issue comes with the accessories themselves. Quality accessories are very expensive. There is no getting around that as you get what you paid for. On top of that up front acquisition cost, you also have to consider the additional operating costs and expanded logistics footprint that will cause.
Even as recently as Iraq II, the US, and UK military in particular, were having serious logistics deficiencies with basic stuff like body armour and batteries. This was before powered accessories became common place, and vital equipment like NVGs were sometimes rendered effectively useless by a lack of batteries.
All of that cost is simply not necessary or justifiable for accessories that don't get used most of the time.
As far as I can see, the only really useful accessory the PLA could implement would be issuing optics as standard on their rifles. Even then I would prefer normal optics to the fancy powered red dots and ECOGs. Ideally, I would like a side flip mount so s shooter could quickly switch between the scope and irons, but its not a must.
Beyond that, I don't think any accessory is a real need, more of a want. But I would priorities funding for things like NVGs, body armour and personal tac radios for all troopers before allocating funds to accessories.