It seems like you thought "redesigning the calendar of every single organization in the world" meant re-printing the shifted dates when it actually means doing all of the work that has to go into scheduling events.
You also missed: "From simple mortgages to complex financial derivatives, he said, calculations could be made much simpler if there were only one calendar to use, year after year."
And: "Hanke said drug prescriptions could be more accurate with a fixed calendar, sports teams could have a fixed playing schedule year after year, and schools and universities wouldn't have to waste time devising each new academic year."
The rest of the arguments are really just throwaways. Not waste time devising new academic calendars? You're going to be devising new schedules each year anyhow, as the courses offered change, professors change, new students change and enroll in different classes, sports league pairings change, and so on. And the existing system doesn't require re-doing the basic calendar every year; you can devise 14 calendars up front (one for each day of the week, times two to account for leap years), and then do the scheduling within one of those 14 basic calendars. The cost of that is going to be pretty minimal, going from 14 calendars to 2 calendars isn't that big of a win.
Drug prescriptions? People are imperfect; they don't necessarily take drugs precisely and regularly, such that you can avoid all variance in the rate of drugs being prescribed. With many drugs, if you miss one dose, you just take your regular dose the next day, and are now off by a day from the prescription cycle. Or sometimes, people might take a little more of a drug than prescribed, or lose it and need a refill sooner. And drug prescriptions should be reviewed by doctors on a yearly basis anyhow. If prescription systems have to deal with that, there is basically no benefit to be gained from having months and days line up precisely year after year.