While the Xantia itself wasn't any particular standout in Citroën's history, its Activa variant felt like the Citroën engineers had finally broken through the Peugeot penny-pinchers. At least one last time. Citroën used to be about pushing unconventional engineering (like front-wheel drive (Traction-Avant), unibody (ditto), hydro-pneumatic suspension (DS), self-adjusting headlights (SM), active self-adjusting steering (CX), anti-roll (Activa)); the Metropolis - by contrast - just seems like a styling exercise with some conventional (though uncommon at the time) engineering.
Citroën used to push the frontiers of car manufacturing, but haven't done that since the 1990s.
Disclaimer: I own two classic Citroëns, so I'm likely a bit biased.