Highlithed to make the problem clear: People believe that. Believing something doesnt make it true (sorry all religious people out there).
The whole problem here is that the OP and many other people have a missunderstanding of the concept here - the only way unsyching content is making it easier is by basically removing DPS-checks and making mobs hit less hard. Thats bought with adding new "mechanics" as in: dont dps the boss to quickly or he'll wipe you (yes, I consider knowing when not to deal damage a mechanic aswell - not intended in this case, but also not the end of the world as long as you pay attention to what you're doing.)
Unsynch does not mean "here, get this kill for free" - just as much as queueing for any content in this game, however you do that, means that you'll 100% clear it. If you clear it or not, is up to you and your party in the end.
The feature exists to give players easier access to the content, by allowing them to go in with a smaller group and still clear it.
If you dont want a challenge: Go and do any other content in the game - and watch the cutscenes on Youtube, if you want to see the story. They've learned with Alexander and we're having that "easy mode" you're talking about now. "Easy mode" isnt as "easy" to make as you might imagine though - and revisiting that old content is not going to happen, most likely. Infact, the content already got nerfed - leave Coil as it is now. And dont confuse "Unsych" with "faceroll" - you dont tick "make this content faceroll easy" you tick "dont put me on level 50".
The more and more threads and posts like this I see, the more I feel people are having a wrong idea about what it means to "be able to do" certain content. We all have access to this content, once we've unlocked it - and honestly, thats all the game has to provide for us: The option to do this content. A lot of times I'm reading stuff like "Oh, I cant do this content, because no one is queueing for it/all the parties suck - it has to be changed!"
Now, thats only half valid as assumption - there are certain contents where its a problem if no one is doing them (all storyrelevant content, obviously - but thats what we got roulettes with extra boni for). This doesnt apply to all content, however. The game does not have to give you the people you can clear, or even just do, this content with - it only has to provide the content. If a large portion of the ingame content is unapplying and no one wants to do it, thats obviously a problem - but for certain contents there is actually a good reason to make players go through a few more hoops, to clear/do the content: difficulty.
Coil, aswell as Alexander Savage isnt even designed with the intention that everyone is going to clear it - they have certain number-projections of people who will clear the content and if those dont match the actual numbers in the end, the next raid will get adjusted. Not everyone is even supposed to clear Coil! And I'm not saying that because I'm feeling special about having cleared it, I'm saying this because you have to understand that this content is "special intrest" and is designed with a group of people in mind who will work together, often over weeks or even months to learn those fights and get them down. Thats something the dev-team wont ask of everyone whos playing the game, obviously - but its something that a certain group of people is asking of the game because they enjoy that.
Its really not so different from a certain group of people enjoying crafting and gathering - and getting exclusive content for that.
Think about it this way: I would like to win a marathon - now, can I do that? In theory: yes. I can go and register for a marathon and the compete in it. Practically: No, I absolutly can not - because I'm no where close to the shape and fitness you'd need for a marathon. Now, what do I do if I still want to win a marathon? Do I go and train and get myself fit for it? Or do I go to whoever is in charge of marathons and ask him "Listen, 42km is waaaaay to much, no way anyone can run that! Cant we make it like 4km or so?"
Here is a really simple answer: Variety. More than one challenging content. We have tones and tones of more casual-friendly content, why shouldnt we have at least a slight variety in challenging content aswell? Just because its old doesnt mean it has to be removed (nerfing it would be the same as removing it for people who like to have a challenge) - by that logic we could just get rid of all level 50 dungeons that arent relevant for the mainquest.
Its a good thing that the game is growing - and there is absolutly no need that the "difficult content section" shouldnt be growing aswell.