While I'm the first to admit that there are plenty of aspects of JFK T4 that are lacking there are signs indicating the direction to the departure gates right after security.

Since all departure gates require passengers to go down this one level this seems reasonable to me.

Then, once passengers are on the lower level, there are a couple of options to get to the gates depending on which airline they're traveling on, although all DL flights in T4 are on the B concourse.

To me, the bigger problem at T4 (which I fly out of often) is the fact that the B concourse is so long. If you have checked bags, for example, not only do you need to walk the entire length of the concourse, but then you need to walk to the north exit of the terminal in order to gain access to baggage claim.

Also, although T4 is Delta's flagship terminal at JFK, it is shared with a number of international carriers as T4 is the airport's international terminal. If you are unlucky enough to depart around the same time as a Singapore Airlines or Emirates A380, security can be very long, especially since, for some reason, for many hours during the day, TSA operates a pseudo pre-check line, where non pre-check passengers are mingled, thus slowing down the process considerably.