If you're only ruining your own experience, then it's only the fact that it's against the Terms of Service, and exactly what Yoshi-P said, don't advertise the fact that you use it or that it exists at all.
There could be 1000 raiders using it this way, but the minute one of them they start talking about it being some kind of requirement is why these tools should not exist. Not every fight in the game is a DPS burn, and by giving the illusion that your DPS numbers matter like it was a competitive environment sucks the fun out of the game for others and players then shun the hard content because the raiders have given them the picture that the content is impossible and they will be kicked for even trying.
And this just proves what I said above. The tool should not exist. People using it should not assume others also use it, and the minute they do, they've crossed the line from "personal use" to destroying other players enjoyment of the game.
This is not a "guns kill people, people with guns kill people" semantics thing. The analogy is people being given loaded guns and people who don't recognize them as guns start shooting people and then don't want to be held responsible for the consequences.
Because the people who develop the tool have no interest in preventing abuse. A tool is just a tool, and you just reduce adoption of if you try to prevent the bad actors from doing bad with it. The harassment isn't confined to the game either. Twitch, Discord, Twitter, Reddit and other forums that are below SE's radar are other means of harassment that SE won't do anything about.
History is rife with "It doesn't affect me, so I did nothing" stories about how small annoyances became large problems seemingly overnight because nobody spoke up when they saw a problem.
If someone released a "DPS meter" stand-alone from ACT, with no plugin capability and simply replicated the common popular parser overlay, do you think people would dump the ACT plugin? No. They won't because the ACT plugin lets them do things beyond it.
That is just human nature. People will not accept a replacement for something unless it does something "better" and a simple DPS meter is not "better" for these people.
So don't fool yourself into thinking people advocating for parsers would willingly give up any privilege once they've been accustomed to having it.
People won't give up a tool once they've discovered it, and instead will trade it for a better tool that offers more so they maintain their advantage over others. SE released the Duty Recorder. So far I've seen nobody use it, because it's not what the parser users want. The fact it doesn't persist past a maintenance also tells me that it's directly tied to replaying the combat data the server recorded, and hence the data is not compatible after a patch. SE needs to do better.
That Duty Recorder should be automatic for all synced duties, and the Opt-in/Opt-out should instead anonymize the players who haven't consented. eg Replace party members with the Scion NPC models. If you don't consent, then playing back your own fights will just not be available, and other players you play with will have your character replaced with a storyline NPC relevant to that content if played back. The server would have to do nothing more than replace your id number with the NPC id number.
All FFLogs would have to do to have a proper consent system would be to not display the names of players who haven't opted in. The actual parsing tools should be scrubbing player data that has no consent to it (eg replace the player ID numbers with random negative numbers to indicate they've been scrubbed.)
The person who runs the FFLogs site makes thousands of dollars from Patreon, and are also running ads. They're not a charity, it's a for-profit venture. They have no incentive to make it opt-in, because that just makes it less useful. Hence this is why you see a push in the EU to have EU citizens data strictly opt-in and the data brokers connected to advertising are having a fit. It's simply impossible to get consent and have meaningful data. They can scrub the identification info, but if the data broker isn't allowed to even log the activity in the first place, the entire dataset becomes useless.