Maybe it's because I'm really bad at socializing (and expressing myself with words, so sorry if I come off as weird all the time), but I find it extremely unfair if I have to run the content for someone who only presses like one button, while I and the others in the group are doing things all the time. Even if the DPS doesn't use his perfect rotation, if he's putting in some effort it's totally fine with me. But a not new healer that only uses heals even though the tank is almost at full HP all the time anyway isn't. Why is is alright for the healer to just stand there? Because it seems to be alright in some other games. Because in some other games he HAS to press the heal buttons constantly. So he only assumes instead of thinking and observing (or outright refuses to adapt), and doesn't adapt his accustomed "playstyle" to this game.
I never played an MMO before this one. The first class I played was Conjurer. I saw I had DPS spells and enemies only removed so much from HP bars. Of course I was very careful at first, but I used DPS spells from the beginning. I think that if FFXIV is your very first MMO or even RPG your even less prone to just healing, because your not used to the heal-only role of some other games.
I have to add that if someone is totally new and doesn't DPS as healer I'm really fine with it, because he must first realize that healing isn't needed all the time. Maybe he doesn't have good gear in his first dungeon and the tank is inexperienced as well, so he HAS to use his heals. But he is able to realize after a while that he would just stand around doing nothing if he only heals in a "normal" party.
And to the first post you made that I quoted, with the "play other games", this is almost all the time only meant for healers from other games that refuse to adapt, not to the new and inexperienced players that are still learning. But the ones that deliberately just idle instead of doing something, full knowing that this game is designed differently.