That's all well and good but the vast majority of content in this game will not require you to perform well. Unless you're going into the latest Savage or Ex fights within a few months of release, you could be doing terribly and still get rewarded with a clear (provided your healer is healing and the tank is at least trying to hold aggro). People get a rude awakening with fights like release Shinryu NM because you can't just Netflix and chill through the whole thing, you have to actually pay attention and try. At that point they feel frustrated and blind-sided because the game never forced that on them before. For those of us who do the hard content and have already sought out how to be good at what we do, it's no big deal. For the people who have no interest in high-end content, it's a rude awakening because not once has the game even hinted that they might want to seek self-improvement. You just get echo stacks until you brute force your way through it with stats.
SE should do a better job of telling DPS players how they're doing. What standards to use, and how to do it, are definitely up for debate. But there needs to be more feedback beyond eventually killing your target before everyone dies of old age.