You are talking about people that already perfom at a high level, they can tell you they are clickers, but do you really know how they play? There is certainly a difference between clicking some abilities that you don't use that often, or clicking your entire rotation, that must be so exhausting i can't even imagine that.
I highly doubt a high end player clicks all his stuff, they most likey use a mix of some keybinds for their core skills and click the rest like most people do.
I had one guy in my static raid in shadowbringers that clicked most of his stuff, he so often failed at mechanics where he had to move quickly it was very noticable, and when i found out he was clicking, it clicked

with me why he made so many mistakes.
Even when it is viable, we are not talking about the top endgame players than can do it, but the low end casuals that struggle with easy & normal stuff because of it.