That was true for defending night fighters, but offensive NFs (over Germany, and Japan) rarely had GCI to help them. Also, even defensive NFs often prosecuted contacts they made on thier own.
As for the various models, you have to remember that each had a role. You can't give the USN a P-61 (or a Mosquito) in 1945, its not CV capable, so the F6Fs and F4Us had their part to play (they fit on the deck), which was defending the Fleet at night, as well as doing offensive ops over enemy territory.
Nothing wrong with the P-38M, it had the advantage of being faster and better performing than the P-61, so it could close a contact quicker, so its not like it had no advantages. The P-61, P-70, and Mossie, and Beaufighter (whos radar operator was behind the pilot), had larger, more ergonomical crew quarters, dedicated radar operators, and larger radars, so that was their advantage.
...they all had strengths and weaknesses, and sometimes different roles.