Great Britain and England will never improve unless there is money put into the non-heartland areas. I have posted about this in another thread.
However it is silly to dismiss the whole squad. The demise of both Samuel Burgess and Sean O'Loughlin in the same year has been a huge blow to the team's morale. Also the presence of Thomas Makinson, Mark Percival in the outside backs, and Samuel Tomkins (who was a star of the Downer Nines) in the halves, would have given the team a much better capability in attack.
It would be silly to dismiss John Bateman and Elliot Whitehead, who are both quality players. James Graham is getting on in years, but still deserves his place and the captaincy. Thomas Burgess is also okay, even if not great. We can hope that Luke Gale will be uninjured and recover his form of 2017 when he plays at Leeds next year. Those players could provide the core of the senior players in 2020.
It is worth contemplating that if France was given the chance to strengthen its roster, by having Toulouse in Super League, and Avignon at least in the Championship before getting promoted to Super League, and if England played at least two games a year against France (one in England, one in France), then the quality of the England team would also likely improve. The astute Ian Lenagan has suggested as much. But this aspect of development is going to take a few years, even if Toulouse joins Super League in 2021, which is not guaranteed.
A stronger England and France, with the possibility of a strong Canada and USA in ten years from now, would rejuvenate the international game. We cannot rely on the South Pacific as the only place for developing the game, because the Pacific islands, including PNG, don't have the financial resources, population, or sponsorship money to make the international game more profitable. The northern hemisphere is the region where the money and people are.