Unless you think tourists will just decide to skip Paris, they are going to substitute some way of getting around the city and seeing at least some of the places they want to see, even if it's an imperfect substitute. A guided tour is one way, exploring on your own with a guidebook is another.

There may be an argument here about induced demand: more capacity results in more tourists until it gets too inconvenient at some higher level of visits, and similarly in reverse. But this suggests that removing capacity will result in bottlenecks due to traffic somewhere else. Things will get worse somehow until the word gets around and people reduce the number of trips they make.