"heritage" isn't about fashion, Citroen is signaling a specific value proposition and ethos through this choice. And also enough commitment to burn their one throw at this target.
They already went a similar direction with the Ami,it was a pretty bold move and it was met with very decent sales https://www.passionnement-citroen.com/post/citroen-ami-premi...
Also Renault 5 and Renault 4 seem to be selling quite well.
Ami-style cars are toys for "rich" people. No lower-class or lower middle class person who can only buy one car is going to get it, since its compromises are too great; tiny range, lack of AC, no suburban or highway capability, can't fit a stroller or child seat. That person will inevitably get either something like a C3/C3 Aircross/Clio/Sandero or a Chinese EV like the 20k euro Geely E2 or Aion UT or 16K Leapmotor T03/B10 or 18K Dolphin Surf.
An upper-middle class or "rich" person will get one, as a third car for errands in the historic center (doesn't wanna mingle with the poors on public transit), as a first car for his 16 year old brat (a travesty that law allows it) or a runabout for his wife that has old her car license due to drunk driving.
The Ami is very popular around here. Lots of high-schoolers driving them since they can do it without a (proper) permit.