Air taxi Captain reported an NMAC near JPX and requested a new evaluation be taken for this area regarding a full-time Control Tower.

Narrative

Our destination JPX is an uncontrolled airport (part-time control tower in the Summer season only). The winds were light but just slightly favored runway 10; and this is what runway we requested due to the short runway length there.Our aircraft was a few miles east of the FOK Class D airspace at 3000ft. We were being vectored towards MATHW waypoint for the RNAV Z Runway 10 approach. The ATC frequency was very busy; and I observed numerous TCAS targets on my MFD (Multi-function Flight Display) in the area around and below us. The aircraft that caused the conflict in this episode was approximately 5 miles in front of me; between my 12 and 1 o'clock position at 2500 ft when the controller instructed us to turn right direct to MATHW; and very shortly thereafter cleared us to descend to 2000 ft. I had some concern about that target; but the frequency was too congested for us to question the course/intentions of that target. Just as I was starting my descent; this target started to climb and appeared to be moving toward our airplane; causing an immediate RA command for us to climb; and we complied without delay. The TCAS was instrumental in helping to prevent a collision; because: 1)I never visually acquired the target; and 2) It was at least 5 seconds before the controller could issue deconflicting instructions due to frequency congestion.Ultimately; we were instructed to return to 4000 feet and vectored northwest away from the cluster of traffic in the space between our airplane and the destination airport. Subsequently; when the frequency congestion cleared up a bit; the controller suggested vectors to the opposite runway; as he was observing that other VFR airplanes appeared to be maneuvering for that runway. This would have been more useful for us to know earlier in the arrival; but again; just too much traffic and frequency congestion in the area for the PNF to be off frequency for any period of time to sort out what seemed to be a very fluid situation at the uncontrolled destination airport.I think it relevant to add I was astounded by the density of traffic in the proximity of our destination this day. I have flown passengers commercially for 20 years and cannot recall seeing this level of density and traffic mix (small GA; helicopter; and jet traffic) at an uncontrolled airport simultaneously. The overlying airspace is Class E with no regulatory requirement for VFR traffic to be in direct communication with ATC. I have flown in Class C or TRSA areas with less traffic than was operating over the eastern portion of Long Island; NY today. It also strains belief that JPX only operates a control tower during Summer months; today there absolutely was enough traffic at this field and in the immediate surrounding airspace to warrant a local control tower.