How to get rid of the Mods and go back to vanilla Anno 1800?

If you want to play without mods for a short time only, it is sufficient to rename the folder mods. The Mod Loader will not find any mods when starting the game, and the game will start without mods.

If you want to free your game from modding permanently, you have to delete both python35 from the mod loader and replace them with a backup of the original. But you can also make Uplay do this for you. The function can be found under Games => Anno 1800 => Properties and it is called Check files. But you will have to delete the folder "mods" yourself.