See, it's lines like this that make people really want to disagree with you.
Believe it or not, not everything has to be exactly 0 or 100% (except this group's percentile in this case ofc!)
But they are though?
Pick any one Resto Druid ability and try to clear dungeons and casual raids with it. It just wouldn't work.
Meanwhile in FFXIV, you could easily clear Normal Modes, 24 mans and arguably even Extremes with just medica II. Dungeons would ironically be a little tougher needing the tank to cooperate with cooldowns on trash pulls but that's certainly not that steep a challenge either.
So what's the difference here? It's the nuance within the healer's toolkits IMHO. WoW had a greater emphasis on combinations of abilities adding up to make them greater than the sum of their parts. Of course not every healing class was perfect in this aspect, but it's plain to see that the regular favourites tended to have the most emphasis on this. Other MMOs that are regularly touted as having good healers also similar in this regard, SWTOR and Warhammer Online being particular favourites of mine. The healing kits were tightly designed with a ton of interaction between various abilities and resources.
FFXIV has very little of that and what interactions it does have are merely 'press this button for more healing for x seconds' with the only complexity really being remembering what's a spell vs an ability.
Compared to WoW, Swtor or Wol, FFXIV's healers are badly designed, no ifs no buts.