I've played on and off FFXIV since HW I have every job except dancer and monk capped.
FFXIV combat is janky as shit, slide casting, animation locks, (o)gcd clipping, server tick nonsense, the telegraph engine issue. That's all without comparing the game to wow.
Comparing the game to WoW, ignoring the above the game 'feels' less fluid because of how WoW handles how you see combat client-side compared to FFXIV (this is why people often describe FFXIV combat as floaty).
Does that mean FFXIV combat is 'bad'? No; I prefer WoW? No. But that doesn't mean I run around denying the truth.
Anyone who thinks FFXIV's combat is 'fluid' has either never played wow, doesn't understand what people mean when they say clunky/janky/floaty (which is fair most people don't think about this stuff and resultantly don't have the vocab or technical knowledge to explain themselves properly), or won't hear a bad word said about their baby and will actively attempt to shut down any criticism.