Well, you're very anti-Paris for whatever reasons, so I can't say I'm surprised by your response. Obviously, I disagree. Park Monceau, Montsouris and Andre Ciroen are quite, quite wonderful, and much more imaginative than most London parks ... I also fail to see quite how somewhere like the Luxembourg Gardens do not constitute being a 'real' park. Personally, I find it easy enough to chill out in the stunning Place des Vosges, which is probably one of my favourite places on earth.
Quite simple. No grass to sit on, mostly consists of gravel and metal chairs, basically not somewhere you can go to relax.