So what happens after the eldritch labyrinth in terms of plot? 6 years ago if memory serves me right there was a last update to things concerning plot, or a thing. I don't remember anything being terribly different in the different ports to 1.8 or 1.12.
IIRC, there wasn't much to do after exploring the Eldritch Dimension, defeating its boss (there were 4 different ones you could encounter, though only one of the 4 were found in each dungeon), and obtaining the Primordial Pearl. The latter was used in the crafting of the Advanced Alchemical Furnace.
Now if you had Thaumic Tinkerer 2, it was usually at this point you unlocked the KAMI module, which gave access to more powerful wands, weapons, armor and tools, as well as a dimension where you could mine large amounts of ores (the Bedrock Dimension).
I know there wasn't much to do after exploring the eldritch dimension, but isn't that kind of the point of updating the game? Thaumcraft 6 added custom wand foci, a gauntlet instead of a wand, rifts that made flux a bit more threatening and even added a bit more to the mod's lore, which is something that I liked about it when compared to other mods. Thaumcraft told a whole story, which over time expanded.