Thank you so much, that explains a lot.
So casual more refers to players that preferred to heal and not dps much, if at all. It was kind of the way the game expected you to play most of the time too(with some decent reasons to, even), so it was still a viable playstyle even in hard content. That's wildly different from how I was thinking about it.
It seems pretty natural for the devs to then want to make hard content with healer dps accounted for. It also would make sense for them to not want to shut out the above players from being able to reach clears because of that and started simplifying it a little in SB, but I'm guessing it still wasn't received well at all since they ended up pushing it much further in ShB.
I have the impression a sizeable chunk of JP forumgoers were from that camp, considering when I asked them about the 1111 gameplay 2 years ago
(link), the responses I got were largely some variation of "it can't be helped" or "it's right where it should be". I also recently wrote a thread
(link) suggesting making healer DoTs 15s with subsequent uses extending its effect time up to 30s, which I thought could add a nice mobility/weaving option, but I also mentioned it'd make the dps-ing less mindless, and they kinda laser focused on that almost immediately, trying to write it off by saying they "don't need damaging tools distracting them from their heal work". It's like they're terrified of it becoming anything more than it is now.