FTFY I don't depend on Forge, I depend on a toolchain which includes (up until now) LaunchWrapper (a Mojang product written by cpw) and ForgeGradle (a modern build toolchain which was designed for Forge but is basically the contemporary MCP) and Mixin (LiteLoader's core which was extracted and improved to power Sponge and other mods).
LaunchWrapper has been supplanted by ModLauncher (a new project written by cpw to address the shortcomings of LaunchWrapper) and I am having to update Mixin to support it. I am also folding in some internal improvements to the structure of Mixin in the process, since the adoption of ModLauncher has necessitated some significant changes anyway.
All this is taking time, LL will come to 1.13.x but it's just taking time. We haven't had changes of this magnitude in recent years and this is taking considerable work to achieve.