The Jets needed a cover safety (ie, free safety). They signed two FA whom, on their best days (which may behind one because of injury and the other because of age), were NOT very good in pass coverage. In other words, the Jets' weakness at safety remains. They remain especially vulnerable to the big, fast TEs that are becoming popular.
The Jets need to stretch the field. The two WRs they added, Schilens and Hill, might work out or they might NOT. One has done nothing because of injury and the other one is a rookie project. Although they're fast, they've got to prove that they can get open and make catches downfield before NFL DBs take them seriously.
The Jets need to improve their OL. They have replaced two top OLers at key positions, LG and RT, with two guys who are essentially backup quality. Vlad Ducasse has been disappointing. This particular draft had lots of OL talent of various quality and skill levels, so finding some shouldn't have been so hard for the Jets, but they only managed to find an OG in the 6th. Pitt probably snagged a likely perennial Pro Bowl RG in the first, the Fins grabbed a RT in the second or third, the Bills grabbed 3 OLers (a LT in the 2nd, another OT in the 5th, and a C/G in the 6th).
The Jets don't really have the personnel to be the run-first, ground and pound team they want to be. They don't have a dominant OL like they did in 2009. They don't have a good OL and a good starting RB like they did in 2010. Shonn Greene is a mediocre RB who doesn't have a lot of speed, break tackles, make guys miss, change directions/cut back very well or have particularly good vision. He's mediocre, especially as the starter. Oh, yeah, the Jets don't have a traditional blocking TE, something that's essential for a successful run-first team, especially one with a RT named Wayne Hunter as its starter.
It's nice that the Jets added a pass rusher and a LBer and some late round safeties, but their defense was already much better than offense. They did very little to get Sanchez better protection and targets, and then undermined him further by bringing in Tebow.