Which promotes an actual change in tactics over the standard "pull entire room and spam your aoes." Granted, getting DPS players to even do that can be asking too much lately...
Wouldn't it be nice if Leg Sweep actual had a use? Or DPS were meant to take down this priority mobs so they don't overwhelm the healer? And wouldn't this diversifying gameplay necessitate more healing, thus giving healers more to do that isn't damage. Furthermore, contrary to your bias persistence the only way content can ever be harder is through OHKO attacks. Here we have an example—one you provided—which doesn't do that.
And you seem to forget Zurvan Extreme is midcore content, i.e, endgame. I reiterate, you have no business joining an EX party if you cannot perform a "basic opener." That is literally asking the bear minimum for harder content. An equivalent would be taking an advance computer programming course despite having no idea how C++ or SQL work then complaining it's too difficult. Should we dumb everything down because you took it upon yourself to skip ahead? If you can't perform an opener, why are you joining a Zurvan farm party?
Because you (generalization) were lazy.
As for the forums claiming everything is easy. You're inferring nonsense. Thordan, Sephirot and Nidhogg are all talked about as fairly challenging EX Primals; the former two being highly praised. Even Sophia, generally considered one of the easiest HW Extremes still garners praise for her mechanics. Despite being the easiest tier in HW, Creator is widely considered good; with Cruise Chase and Alexander Prime both being highlights. Even Halicarnassus, Ex Death and Kefka are well liked.
None of these fights are considered faceroll, Sophia notwithstanding. You're simply blinded by your own bias.
Have you considered, you know, not doing that? Everything you described is easily remedied by adapting to the situation and learning. Experiment with what you can get away with. Did the party actually need that extra Medica when the aoe damage barely did 40%? No, Medica II will tick them up just fine. You're only a worse healer if you stubbornly stick to a preferred method even if its proving less efficient. Overhealing and dealing less DPS tends to happen when you don't yet know a fight. I overheal plenty because I haven't figured out all the timings. Not to mention, I have to adapt to players who are equally unprepared or new. With practice and repetition, this becomes easier. Regardless, you're forgetting these players already experience what you described except instead of a progressive difficulty curve to better ease them into EX and Savage. They see a sudden spike because FFXIV typically does a horrible job pacing.
If everything stays easy, people become complacent, which is what results in the sudden shock when you try moving up a tier and nothing you've done works. This is why we see people whine about Shinryu normal. The game conditioned them to expect a casual stroll, then ramped up the challenge seemingly from nowhere.
Nonetheless, you are correct some people won't rise to the occasion. Better they quit at Alphascape than breeze through an easy alternative only to get blasted by frustrated people in Sazaku EX because she's a sudden jump.