It really is not a real criticism, out of the 30-something abilities on my dark knight only 5 abilities are even on the gcd. The APM required in FFXIV is a lot higher than WoW, even before legion, even back in MoP the rotations were faster. Also the actual rotations are pretty complex and require effort to master instead of lol 5 buttons.
Using the 2.5 second gcd argument is the same as using the gender wage gap; its been utterly debunked a million times but people continue to use it anyway for whatever reason