Epidemiologists existed in 2000 and were quite capable of recognizing the difference between a global pandemic and "a really bad flu season".
Hell, the 1918 pandemic literally was flu, unlike COVID, and it predated a lot of what we think of as modern medicine, and it was heavily censored by governments around the world, and it was still obvious that it was more than just "bad flu season."
Those who compare COVID to a really bad flu season don't seem to understand just how bad a bad flu season can get. The estimated deaths from 1918 are thought to be 17-100x what COVID has caused so far.
For some people, maybe. For others, it's merely recognizing and stating that we've gotten through bad or even worse epidemics than this. Often without the sensationalized hoopla. Eg,1968.
I'd argue it's the people saying it isn't comparable to a bad flu season who are the ones less familiar with the flu's devistating history.
The fact that we've gotten through worse doesn't mean it's not a major issue. There's a large gap between "human civilization will survive this" and "not a big deal."
Hell, the 1918 pandemic literally was flu, unlike COVID, and it predated a lot of what we think of as modern medicine, and it was heavily censored by governments around the world, and it was still obvious that it was more than just "bad flu season."