I hear what you're saying Ryan - although in fairness there is some history there, and also some very significant challenges on all sides to actually communicate. However, one has to keep in mind that sometimes the definition of "end user" can be pretty different. On reading this thread, I have the sense that lots of people commenting here see template creators/curators as the "end user" - but they aren't in any conventional sense. The end user is the person who actually uses the template.
The end-users for scribunto are template editors. The way the template is called from articles is almost exactly the same. The syntax is so similar to how it currently is that It does nothing to change the experience for a normal editor.
I'd bet that most templates will keep the same arguments when switched over, and the syntax will be mass changed by a bot.
- Ryan