That which Lua is missing is primarily in terms of its ability to define clear, succinct algorithms. And in this respect the more Algol-derived languages enjoy a substantial advantage by having readily available tools for the task. Tables are a semantic compromise compared to list, array and map primitives, and the standard library assumes little, making it hard to write "native" Lua without encountering a need for R&D on some dependency.

But when it works in its true intended domain, gluing together and applying configuration to structured APIs and data, it's about as good as it gets, having had the benefit of major revision. And that makes it a stable computing platform, even more stable than the Lisp family(which are like BASIC in that it's quite easy to make an incompatible one). As a side effect, that also makes it an excellent source-to-source target.

But to put it another way: Everyone says they like minimalism until they try to live in it. Everyone who needs minimalism knows its limitations and makes exceptions.

That's exactly what makes Lua and JS directly comparable - they're both barebones, when it comes to stdlib.

But as far as the language itself goes, Lua is far superior, with a lot more consistency all around, and fewer traps.