I disagree, you need pure talent at NT for this defense to function, overall these guys don't rack up lots of stats but they are the big reason their teammates are able to make plays. Then you need stout guys at DE that can hold their ground.
Casey Hampton is one of the main reasons this defense is that good. Keisel and Smith are his DEs, solid but unspectacular.
Jamaal Williams for the Chargers, too, though the last couple of years he has been battling some injuries, he along
Hampton are two of the best. Castillo and Olshanky are the DEs.
Vince Wilfork for the Patriots, he along two other first rounders are the reason why they can plug anyone behind them and still make plays. Jarvis Green has been making plays for them at DE, very underrated player.
Haloti Ngata is elite, without him Ray Lewis was constantly blocked by a lineman. He implored his FO and coaches to address the situation and they drafted Ngata.
Jason Fergusson, while he's not elite he is a big reason for Miami's defense turnaround.
The Jets didn't have the talent with Robertson, this year they brought Jenkins and that defense imroved a lot, but because he's not a pure NT that defense faded away at the end of the year.
Other than Ferguson those guys were drafted in the early rounds. Williams was picked on the 2nd round of the 1998 supplemental draft, Hampton, Wilfork and Ngata were drafted in the first round.
If you don't have a good NT it's not an easy defense to build. But still I like this defense better than the 4-3 defense.