While there is tons of nice place/stuff to do in Paris, many people see it as a perfect, romantic, ideal whatever city, and a visit there the trip of a lifetime.
Paris is a 10 million inhabitants urban area with all the associated problems,
Imagine thinking you’re in the perfect city and being stuck in a crowded train, then in traffic, and falling in any possible tourist traps, from the barely legal but legal low quality, high price restaurant to the pickpocketsand other petty crime
Mobilizon is a federated group/event platform
On my area meet up and Heylo are popular group/events platform, but both are proprietary