Pro 18:17 The first to put forth his case seems right, until someone else steps forward and cross-examines him.
Attempting to discern the dates of the literature in New Testament is in many ways a fools errand.
It has some value, but not a great deal. For instance, if James Crossley or David Alan Black are right about how early the earliest gospel is (they disagree about which it is), then many of the arguments against the reliability of the general outline of Jesus’ life in the gospels are pretty much false. At least if they are of this form, “The gospels are late, therefore the gospels are fictional.”
Dating the texts can help to understand some of them slightly more accurately. For instance, the order of the Thessalonian letters might help us see if and in which direction Paul’s thought changed over time.
Over all, the evidence available is the same for everybody and the syllogisms and arrangements of that evidence as well as comparisons with all of the important historical analogs seems to have been accomplished. I’m not saying there isn’t a truth about these topics out there. I’m saying that one or several scholars may have discovered it, but since the evidence is incomplete, the arguments are not compelling. Thus, as the Proverb reads, “The first to put forth his case seems right, until someone else steps forward and cross-examines him.”
This does not mean people should give up. Seriously, I have my own, perhaps unpopular view of the dating of the New Testament. I just mean that until new evidence presents itself or a truly creative argument arranges the evidence in a probative way, we’re basically stuck with enough certainties to make a broad outline that has tremendous plasticity within its borders.