There are many effects going on concurrently which make xiao long bao (soup dumpling) amazing:

Pork Xiao Long Baos!

Skin Texture:

At a high level, the skin of the xiao long bao (XLB) has to be thin. At world biggest food chain, Din Tai Fung, their recipes uses for 5 gran dough requirement. In additional, you want the moisture level to be at the right levels such that the dough doesn't become too sticky.  The wrapper/skin has to be strong enough to hold a healthy amount of soup without leaking or breaking when lifting out of the steamer basket. The thin thickness can be a low as 0.72mm (from online sources).

Meat & Fat Ratios:

Din Tai Fung uses exact 16 grams of ground pork filling with the combine gelatin soup base (soy sauce, Xiao Shing wine, salt, sugar). The texture of the meat really matters. I have tasted XLBs where the meat is steamed enough that meat inside becomes like a semi rock (not a good thing). The idea is to slurp the dumpling in one bite (once cooled). Pork has been the traditional fillings but recent modern restaurants have been adding their seafood version twist. Regarding the fat content, online sources say at least 25% ratio compared to the meat. The fat will provide the necessary medium for flavour carrier (similar to baking) and softness for the meat.

Did I miss something? Please feel free to comment!