According to Sammy The Bull, thy werent inducting new members because very few of the younger generation were all Italian. Most of the 2nd generation Italians married non-Italian women [probably southern women from NO ], and therefore their kids werent eligible for induction at that time.
You would think he could have imported some guys from NYC, or even some zips to expand his family but decided not to for whatever reason.
The Marcello Family always had a very small "official" membership to begin with. The borgata counted on a large number of outside associates to augment them. And for many decades it worked. But as Carlos and his top men aged and died off, he never inducted new blood.
Why that is is anyones guess. It could be a number of things; he just didn't wanna do so; there weren't enough available "Italians" who Marcello felt were groomed and capable of stepping into their tradition; there were too many "half breeds" (although I'm not certain that played into it because even by the mid-1970s when NY opened the books there were many guys brought in that were not full-blooded Italians (I personally know of several).
But understand also ML that the New Orleans crew was not alone in their thinking. Its the very same process and mindset that led to the demise of many borgatas throughout America. A lot of those old time siggies just didn't trust or care to induct the newer generation. They lived the life and utilized it to springboard their lot, and let the family die of attrition.
Good examples of this was the Pittston-Scranton crew under Russ Bufalino, the Pittsburgh outfit under LaRocca, the Cleveland family, San Jose, San Francisco, etc. The list goes on and on.
Only the largest crews like NYC, Philly, New England, etc., maintained themselves in future decades. And today even those crews are rocking on their heels from a lack of quality recruit, as well as, a shrunken membership roster.