Pretty much the only advantage LT ever had over Emacs was the GUI layer unburdened by decades of development and compatibility with TTYs. In other words, the hope for LT was that it will allow a wide range of scriptable graphical effects. While never explicitly stated, if you read early posts on LT you'll see its feature list is basically 80% Emacs, 10% Smalltalk and 10% eye-candy.

Many (five?) years later, from what I gather, LT has the eye-candy - the rest is perpetually "under construction". It would be hard for it to be anything else, though, as the main developers jumped ship a few years back to work on Eve (which, as a karmic retribution for all my crushed hopes for LT, also tanked and died recently).

Emacs may be less pretty than newer editors, and lots of its APIs are decades old at this point, but it's still the only self-documenting, easily discoverable and extensible editor this side of Pharo and Squeak, which can be used in practice (due to a giant amount of plugins which bring it up to modern standards) for almost any task.

TLDR: LightTable as a powerful editor for programmers is dead - it may be still possible to revive it, but its scope would have to be massively scaled down. It's not going to compete with Emacs & co. anymore, which is a shame, because when it started it had the potential for this.