Firstly, the Paris Commune did use the FRC in 1871 (look up "Germinal" on English Wikipedia), so there is an association with the French far-left in OTL. It is not just some obsolete calendar from the days of yore, with a revolution in 1917-19, the last (small-scale) use of this calendar would have been less than 50 years ago.
Secondly, I just love the new system. As a child (that was when I was 12 or so) I even thought of "implementing" this in my home. I planned to buy an "empty" calendar (with no month names filled in) and filling them in with Vendémiaire, Brumaire, etc. Also, for years, I dated my school tests with the date in the French Republican Calendar instead of the Gregorian one.
And to boot, I do find the system of day names beautiful, simply beautiful. As I am not Catholic, I know little about the Saints' days, but on my tablet and cell phone, I have a widget/app which always shows me the date in the French Revolutionary Calendar. And I also see that it could lead to environmental and/or health awareness if coupled with appropriate campaigns - for example, today is the Day of Fennel. Yesterday was the Day of the Watermelon.