In France at least the level of grass-roots participation in racing is a tiny fraction of what it was 20 years ago. The crowds at the side of the road are much thinner than they used to be as well. I have visited the Tour for over 30 years, and have lived in France for over 6 years, and most French people no longer give a monkey's about the Tour, largely because the whole thing now lacks any real 'authenticity' because of the influence of modern doping techniques. Doping has also undermined many of the traditional themes of the Tour, such as 'suffering and survival' to borrow from Christoper S. Thompson's cultural history of the Tour.
The French philosopher Robert Redeker has written extensively on this point, as in his excellent book Sport contre les peuples. In this he argues that the 'artificial' nature of the performances produced via doping have created a 'fatal distance' between the riders and the spectators, with riders such as Armstrong, Indurain, Virenque and Ullrich having been transformed into fabricated 'Cyber heroes', akin to Lara Croft, 'virtual human beings' with whom the man at the side of the road can no longer feel the sort of intimate association they could with riders such as Robic or Coppi, especially in times when the spectator could see the hardships, misfortunes and toil of the riders as reflections of their own lives. In short the Tour and cycling in general have become, at best, empty sports entertainment and at worst an irrelevance.
Anecdotal maybe, but when I visited a stage finish on Alpe d'Huez about 25 years ago the crowds were 5 deep over the last 5 km. I stood on the same spot a few years back and could have got a place at the road side even if I had turned up 10 minutes before the race came through. This is despite the growth in the number of people from other countries travelling to the race. This general disinterest in the Tour and bike racing in general, largely because of doping, has also been reflect in a whole raft of books and articles in France declaring the Tour to be 'dead'. Things are even worse in Germany where the reaction to the Ullrich scandal was to simply no longer broadcast pro cycling on terrestrial TV!
But many do, and influential newspaper such as le Monde often refer to the cycling using terms such as 'le syndrome du catch'.
I think you are right. The Brits like to think that doping is only something 'foreigners' do, and are for the most part very happy to wear blinkers as long as it is a Brit, such as Wiggins, who is doing well.