To me it seems like an England manager can never really win. There’s so much partisanship, and the rivalry between clubs is so fierce, that people fixate on things of little importance, like a rival player playing instead of one of their own. Was Henderson always the best option in central midfield? Probably not. Was he so much worse than the alternatives that he significantly hampered England’s chances? Almost certainly not. Does it really matter whether he or someone else is the 21st pick in the Euros squad? Not at all.
As it stands, England have arguably been the best-playing side in two of the three major tournaments he’s presided over. Had the margins fallen their way, they would have had a World Cup final (possible title) and a Euros title. They also deserved to beat France, probably the strongest squad in the tournament, at the World Cup. Yes, Southgate has been overly cautious, borderline defeatist, at times considering the talent at his disposal, particularly in not going for it in extra time against Italy. But he seems to have learned from that and adapted.
So, while he has his faults, I don’t see any rational arguments against him being a very good England manager. To me it shows how fickle perception can be in football; if Lady Luck had been kind to him on a couple of occasions, he would be hailed as a national hero.