Nothing is. In fact, you have grasped the fundamental point I am trying to make (see bolded line).
If the argument is "Cactbot lets other people clear content more easily than I did when I did it, and if other people can clear it more easily my achievement is lessened as a result" — which is, in fact, an argument being made in this thread — then it's absolutely relevant. Because my actual, literal point is that "other people can clear a thing I cleared more easily than I did when I cleared it" is going to be true even without mods simply due to power creep over the course of a game's lifespan. Placing value on your achievements in-game only so long as they remain difficult is not going to be a path to happiness, even if Square-Enix found a way to magically erase all mods and third-party tools tomorrow with the digital equivalent of a Thanos-snap. Because, as I said—and you agreed—achievements are going to become easier over time naturally even just with stuff in the game.
When the argument is "someone using these tools to obtain this achievement actively impedes my own attempt to get this achievement"—i.e., PvP hackery, botting for the Ishgard restoration, etc.—then yes, I agree entirely it's a huge problem. When there's only a limited number of the achievement to be had—top 100 in a Feast season, Saint or Beata/Beatus titles for the Firmament, etc.—then anyone doing something to give themselves an advantage is absolutely a huge problem.
But when the argument is "Cactbot's Raidboss callouts make it easier for someone to clear savage content, therefore my clear of savage content is cheapened"... no. There's an infinite number of savage clear titles and rewards out there. The fact that someone else got their Eden mount from E12S using Cactbot for callouts does not lessen my enjoyment of having gotten it at level 80, any more than it does that people are getting the mount now running E12S unsynced at level 90. And that argument is being made in this thread—"are you still proud of your achievement now that other people can get it more easily"—and I will absolutely, categorically state that if you only remain happy with your PvE achievements so long as other people cannot get them, that is a recipe to drive yourself to madness and misery. Regardless of the existence or nonexistence of mods.