Plus that number could easily grow. Just look at First Contact, Picard mentioned how many worlds were members (I forget the number right now),
He says that it's "over 150" but doesn't give an exact number. Articles of the Federation
features the 155th Member of the UFP joining in late 2380. ETA:
It is unknown how the loss of numerous Federation worlds during the Borg Invasion has affected the Federation Member State count. In particular, it is unclear if the destruction of any given world legally equals the dissolution of that Member State, or if those Member States legally continue to exist in spite of the near-total population and territory loss. Given that the Federation Councillor from Deneva and Denevan President retain their offices even after the destruction of Deneva itself (and that the Federation looks for a new planet that will explicitly be the new world of the Denevan people) in TNG: Losing the Peace
, I would infer that those Member States legally continue to exist, with their diasporas still constituting a legal citizenry owed representation in the Federation Council and a territory of their own within the Federation, but this isn't explicit. End Edit.
and then in the next movie, Insurrection, we see that species that had only had warp flight for a year, enter the Federation as well (the species that was right at the beginning of the movie, and were munching on the floral arrangements).
No, the Evorans were not becoming Members in INS. Rather, the ceremony aboard the Enterprise
was to commemorate their becoming protectorates
of the Federation.
A protectorate is a weaker state which allies itself with a stronger state, who agrees to protect it from external threats. A protectorate is still a sovereign and foreign state and may terminate the relationship unilaterally at any point.
However, later novels revealed that Evora later became a Federation Member in its own right.