While the entire season wasn’t cancelled in 1918, certainly individual games were. As an example, the Missouri Valley Intercollegiate Athletic Association didn’t schedule any official games in 1918, due to events related to WW1 and the flu pandemic
I would suggest that it’s not a good comparison to today for several reasons:
1) 1918 was a looong time ago. There wasn’t as good an understanding about risk factors as we have now.
2) The crowds at the games were certainly smaller than they are today.
3) There’s a marked disinclination on some of the players to take the risk. You can pull their scholarships if you want, but you can’t make them play. If enough choose not to play, they won’t be able to field competitive teams.
Not to minimize the impact of the 1918 pandemic at all. 675,000 deaths out of a 103M population is ridiculously high death rate, and one I sincerely hope we will never see again. However, I suspect that the death rate would be lower if they had our level of medical technology.