Air carrier Captain reported difficulty finding taxiway Foxtrot after landing at MSY Runway 11 due to inadequate signage and poor markings.

Narrative

Upon the completion of a night VMC approach to Runway 11 in MSY; we were rolling out to exit the runway north on Taxiway Foxtrot as was the plan discussed in the approach briefing. I observed a direction sign indicating Taxiway Foxtrot on the south side of the runway and that exit has a large filet area and is designed for faster speeds; but I believe it does not meet the criteria of AC150/5300-13A. Regardless; the direction sign is located properly prior to the taxiway and is clearly visible. As we passed the direction sign and beginning of Taxiway Foxtrot on the south side; I began to locate Taxiway Foxtrot on the north side of the runway. As I was searching; I noted a dark; paved surface but could not locate a direction sign. I did note a black and yellow diagonally striped sign indicating an unusable surface. I continued to search for the turnoff and finally located Taxiway Foxtrot on the north side. We exited normally and proceeded to the gate.Upon block in; the initial hard surface I observed was the decommissioned Runway 6/24 and the pavement still exists. The unusable surface sign is unlit and is recessed back from the runway. No direction sign for Taxiway Foxtrot is located on the north side of the runway. I was expecting Taxiway Foxtrot much sooner on the north side as we had past the direction sign for the south side a few hundred feet prior. Upon further study; the direction sign on the south side is located approximately 750 ft prior to the taxiway on the north side. The combination of:1) The south side exit design compared to the 90 degree exit north.2) The large displacement of the western edge of the same taxiway.3) The presence of a hard surface north directly across from the start of the taxiway on the south.4) The recessed and unlit sign of the unusable pavement.5) The lack of a direction sign on the north side indicating Taxiway Foxtrot.6) Night conditions/low light.All led to a high workload situation and temporary questioning of the location of the briefed exit taxiway. In retrospect; the Jeppesen Chart has the closed runway marked and the taxiways depicted correctly. I did not study the subtleties of this intersection to the degree required to prepare for the unusual intersection.I do ask that the airport authority consider the possibilities of:1) Installing a direction sign on the north side of the runway.2) Light the unusable surface sign on the decommissioned Runway 6/24.3) Remove the dark pavement of the old Runway 6/24.4) Marry the exit design on both sides of the runway (I believe this may not be possible due to the close proximity of the ramp to Runway 11).5) Rename the taxiway on the north side vs. the south side.