It's worth noting that Cactbot cannot display AoE outlines for you, at least not that I'm aware of. My understanding is that all ACT OverlayPlugin-based stuff -- including Cactbot's various modules, and also the majority of the DPS meter displays that people use -- renders in a transparent always-on-top window (which is just made to poof when the game isn't active); so far as I know, it has zero awareness of what the game is actually displaying. Yes, it knows what's going on (by virtue of listening to the network traffic), but stuff like "what is your camera angle and how far in are you zoomed" is wholly client-side and not exposed in that manner, so there's no way it could render AoE outlines for you in the game world in a meaningful way.
I have no doubt such tools do exist, likely by modifying the game process (rather than just being an external program that sits there watching network traffic). And I would say those sort of tools which give you information not accessible otherwise in the game are definitely deeply problematic. But something like that goes way farther than anything I've seen folks doing with Cactbot. And while Cactbot can call out mechanics before a human raid-caller, in most cases that's only by a second or two at most (because the "start the mechanic now" message from the server tends to come pretty much immediately before an animation starts).
Now, from what I've seen of a friend's Cactbot setup, I do know it can remember that Mechanic A has happened already which means that the next time it will be Mechanic B -- and based on that it can call it out in advance, yes. But in all honesty, I can do that too, because -- as a raid-caller -- I end up learning how the fights work. If I'm in the second Endwalker extreme, and I see that the Dawn's Mantle/Crystallize pairing is "out and then spread", I know that the next one will be "in and light parties". If it's "in and spread", I know it will be "out and light parties". In both cases, I can call that mechanic well before the animation starts, because it will always alternate the elements.
Heck, I've run the first Endwalker extreme so many times I can see the first two hits of the Cataclysmic Astral Waffle Iron and in like 90% of cases I can call the third reflexively without looking, because there's only a limited set of possible patterns and at this point I know most of them by heart. My callouts thus sound like "One... <pause to spin camera from west to south side> ...A, Two. One-A-Two."
This is why when it comes to Cactbot's Raidboss thing specifically, I tend not to think it's a big deal.
Yes, there are mechanics it can call faster than I will ever be able to -- notably, from what I understand, P3's Experimental Fireplume, where it can apparently call whether it's the big center AoE or the spiraling Shiva-circle type hits way before I have any clue from the animation. (Which, to be fair, I find a little annoying. But whatever.) But I tend to think that balances out because there are also mechanics it cannot call consistently or correctly; every time I see someone blindly following Cactbot in P1S through Intemperance there's like an 80% chance they will die, because apparently it calls it wrong in a lot of cases as it doesn't actually know what the pattern of gems in your square is or how your party resolves it. Similarly, it evidently calls things wrong for Shackles of Time during the Shining Cells phase.
If you blindly follow Cactbot, it will eventually kill you because there's stuff it just doesn't read right; it lacks context, it doesn't know what strat your group is using, etc. Just like if you blindly follow my call-outs, someday I will be tired and say "West" when I meant "East" and kill you as a result. ("Weast" and "Snorth" are perfectly cromulent directions, so there.)
Callouts -- be they Cactbot or a normal raid-caller -- should be a sanity-check on your own read of mechanics, not an instruction manual you blindly follow. I believe that firmly, as I also believe that fundamentally -- taking all the things it does well and that it does really badly into account, at least based on my observations of folks using it -- Cactbot's callouts are fundamentally no different than a human raid caller like me. The bot's callouts are stronger than mine in some areas, yes, but from what I've seen it's also way less competent in others.
Hence why I say "I don't personally care that much about Cactbot, as a raider." And heck, I know one or two folks who have issues that Cactbot solves; I have a friend who is colorblind in a way that he literally can see no difference between the blue/purple and red chains in P1S, which makes Aetherial Shackles really challenging for him. (And, as a result, also really challenging for anyone running P1S with him.) When I've run with him in PF groups, I just make a point to call out his debuff color to him (and then he can read the timer himself), but I know he's started using Cactbot solely for the "which color chain do I actually freakin' have" aspect.
And I'm not going to begrudge him that. (Especially since it means I die to him being out when he should be in or vice versa a lot less frequently.)