Hey Howdy, I was the person who supplied the stats on how many people use Auto-Markers in that thread, but I'll post my 2 cents here.
I am someone who does not use plugins, and I raid with a group of people who are like-minded in that regard. Generally, it does not bother me if people use plugins if everyone they are playing with are O.K. with it. After all, if everyone you're playing with are fine with it, who am I an unrelated person, to yell at you. Obviously when plugins present a problem in a game like FFXIV, it is often when people do it in scenarios where there isn't that collective consent (e.g. cheating in fall guys competitively, or secretly using things in PF without the other players knowing).
That being said, as someone who doesn't use plugins, if they added an anti-cheat tomorrow that worked perfectly with no issues (heck even if that anti cheat somehow magically only targeted the "worst" plugins) it's not like it would magically improve my experience in the game whatsoever.
To that end, I would much rather that they spend the resources identifying *why* people use these plugins and addressing the underlying frustrations and issues that drive people to use them.
Auto-Markers, for example, aren't used for every mechanic in the game or fights they are in, they aren't even used in every Ultimate. They are used because in 3 of the Ultimates there are particularly Janky/Frustrating mechanics that both have incredibly high variance due to things like snapshots and ping and are designed in a way to be frustrating for Party Finder. Often these mechanics, such as Titan Gaols, aren't even the hardest or most interesting mechanics in the fight, they are simply the most janky and frustrating. I would much rather they go in and *change* Titan Gaols to make it better for *everyone* rather than just implement an Anti-Cheat.
We see this phenomenon with a lot of other plugins as well. Some other recent examples I can think of: NoClippy/XIVAlexander rose in popularity after they released an update that made ninja a lot more frustrating to play for a week or two for players who had high enough pings. GShade VFX Filters/EasyEyes had an explosion in popularity (to the point of being mentioned in PF) after fights like Pandemonium 3 were released that were incredibly frustrating to do if you were red color blind.
To that end, rather than spending whatever limited resources they have implementing an Anti Cheat that would just anger a lot of the people using plugins to make their cat faces more yass-ified or w/e, I would rather see them actually adjust content after its released in response to how players play it.