Let's cut the crap lots of crime groups and gangs are thriving in America, just not Italians. It's because they're huge and enormous in numbers, they have the manpower that LCN just can't muster anymore. I still say LCN's downfall is due more to a loss in personnel than RICO or the Federal government.
Numbers are definitely a factor, no matter how you put it. Street/prison/biker gangs get busted all the time as well and in terms of the sophistication of the crimes they commit they're below LCN and in 95% of the time it's related to narcotics, which is profitable but high risk. The difference is that especially street gangs have thousands of young guys that got fuck all else in life and are willing to get into crime to make a living and are willing to deal with all the violence and risks of incarceration that come along with it. Very few make it to the top and once they're at the top it's for a relatively short period of time, but the point is: there's always someone ready to replace the other.
LCN as a criminal organization can not afford itself to operate like that. Not 20 years ago and certainly not now. And yes, this is definitely due to the lack of fresh and hungry blood. They can still recruit and they'll still be able to recruit for a while, but not like other gangs can. Say 40 years ago, there were still thousands of young Italian guys living in ethnically insular blue collar neighborhoods in East Coast cities. By now the majority of those families and their relatives have moved up in the world. There's none of that hunger anymore, most of them are not living in those tough neighborhoods anymore and earning your money on the streets has no longer become a necessity.
Adding to this, the majority of them have also become thoroughly Americanized, and most of the younger members of those very families are like 1/2 to 1/4 of Italian heritage. Intermarriages have taken place with Irish, Poles, Jews...in some (and increasing) cases even with Blacks and Hispanics. They're not Italian American any longer, they're just "American".
Of course, the Mob will still be around for a while. They still can recruit and they still are recruiting. They're still involved in illicit money making schemes and in our lifetime, we're not going to see the end of that. The name "Cosa Nostra" has enough of a mythic lure to it that as long as there is a sizable Italian American community somewhere, some people are always going to choose that path.
In terms of "power" though? Unless the American Mafia is going to start importing young and hungry Sicilians, Calabrians, Neapolitans or Apulians as if they're canned tomatoes, their streetpower for sure is not going to increase and will most likely remain in decline.
