A WoW like situation where mods/addons are required to even get into the raid scene is very much an unlikely hypothetical that could ever happen in FF14 though primarily because FF14 is cross-platform with PS4/5 where they do not have access to any tools like this. Hence this fear is a mute point that won't happen.
On the hand of third party tools on PC, as most have said barring public/twitter NSFW stuff which really urks the developers (for fair and obvious reasons), if it doesn't affect your gameplay, I see no reason why anyone would ever have an issue with someone using a mod to automate combos or something of a similar nature. Someone having ACT up doesn't affect you until they start to give you shit about you're performance, or go into toxic, unhelpful and uncritical insult flinging for your terrible/sub par dps (in their eyes at least). At that point, backlist and report them, and I guarantee they'll get a penalty and perhaps a ban if they are a repeat offender (assuming it is hate/toxicity and not constructive criticism)
Same with things like Cactbot, if they don't clip and kill you by misunderstanding the directions, it just means they die less (hopefully), deal more damage (hopefully) and help the clear go smooth and/or faster (hopefully). It is important to remember Cactbot won't make you a savage raider, and you still need to pay attention to the shorthand's it uses, as well as fight context (directions, buff windows, who's dead/alive, someone else taking your assigned safe spot in a mechanic, etc), well Cactbot ain't going to save you then. Same with any mods to UI, armour and items, clothing, gshade, etc, it is all Client side, not server side, and thus does not affect you in anyway. If the mere idea of other people having fun and having an enjoyable time using addons that don't in any way, shape or form affect or alter your game play experience affects you and irks you inn some deep, weird way, I hate to break it to you but that's gatekeeping and frankly no better then the people who refuse to accept some people mod Souls like games to have an easier time because they like the story/art/style/aesthetic etc.
Sp long as you they don't insult, belittle or hurt people with these, well, Square is not going to really ban anything, even if something like ACT is seen on stream without good reason, and will only take action when the use of it leads to toxicity and or harm (such as a streamer flaming their fellow party members on stream cause of their dps numbers). The TOS says that third party addons are not allowed, but Square does seem to maintain a common and loose 'Don't ask, don't tell' idea. It's the same with the copyright warning when you first open bard music instruments. They are not going to ban someone for playing a Coldplay song in game until Coldplay calls them up and makes a fuss. That's why that, as well as the no addons clause exist in the TOS, it gives them justification when they do take action (or in the bard music case, protection from being sued for copyright).