I can see why you'd say that about bilateral ODI series, but not T20s as many Cricket fans and former pros are now fans of the format and as such it makes sense to have an international tournament, whereas the argument against the CT is that there is already a much better & more important ODI tournament.
WRT bilateral ODI series, the reason they don't come in for such stick is:
a - they serve their purpose in team building etc
b - it is like people don't really target international friendlies in football, even if they think they are a waste of time. They would be highly critical though, if a second global tournament was brought in that was a bit shorter and with less teams than the WC. For many, the ODI series are like the international friendlies I guess. Not me, they are way more important than Tests, who cares that England lost the Tests to SA we are well on our way to an ODI series victory