Let's imagine a mod for your_newest_game: giving it anisotropic antialiasing x4.
In your game, you can enter "Options", click "Graphics", "Advanced", and drag the anisotropic filtering slider to "x4". Then click "Apply" and it's saved in a config file in the game directory.
Meanwhile, the mod finds the configh file and changes the line that reads "GFX_Anisotropic_Filtering=0" to 4.
Would you agree that's rather silly, considering this is within skill of about every user?
Well, now remove the option from game menu. Pack the game files with an obscure compression program.
It took some smart modder to figure out the compression program and be able to create an automated tool that applies modifications inside the archive - without need to repack the multi-gigabyte archive. He released the tool, and another one that allows you to browse the game files, as if they were unpacked.
Now someone else finds the config file, and uses the program to change "GFX_Anisotropic_Filtering=0" to 4 within the archive. Anyone with access to the tools can do this. The actual modification of the game is completely trivial. It's just that even most trivial tweak to the game must be packaged in the same, complex tool as a mod.