I don't see anyone here arguing that. An IFR of 0.35, let's say, would be great news at the same time as it would be significantly worse than the flu. Using bad numbers to come up with a 21% CFR is not responsible, and is arguably fearmongering.
My source for the CFR represents the totality of real information the world has presented us to date.
"A CFR can only be considered final when all the cases have been resolved (either died or recovered). The preliminary CFR, for example, during the course of an outbreak with a high daily increase and long resolution time would be substantially lower than the final CFR."