Of course there are always exceptions but the general pattern of cultural development is that you are ready to face the possibility of alien life when the chance to get out there becomes a material reality. We are talking about a guideline for Starfleet captains when they first become aware of the existence of a new species and have no data on them at all. Suppose Starfleet does not detect antimatter, decides to conduct duck-blind missions and then realize that these guys are ready to welcome alien visitors. Then you obviously initiate first contact.You cannot determine maturity by technological prowess.
The Edo were technologically inferior yet were mature enough to accept visitors from the sky. As were the Capellans. The existence of alien life did not appreciably impact those societies. While the presence of Picard and Troi on a world ready to make their first flight was shook to its core.
By your standards, a mature world would be excluded from the galactic mix because they have no interest in FTL technology.
In the case of first contact you have to err on the side of caution.