The Three Lions surpassed expectations in Russia by going all the way to the semi-finals of the competition, where they led for much of their encounter against Croatia before eventually losing 2-1 after extra time.
England then had the opportunity to secure a third-place finish - which would have been their second-best World Cup result after the triumph of 1966 - but they came up short as Belgium ran out 2-0 winners in St Petersburg.
"We have been competitive, over achieved our landmark and to finish in the top four is probably above where we are currently," Southgate told ITV Sport. "But the players deserve every bit of praise they will get when they come back.
"We have tried to maximize the players we have and their individual profiles. It's not club football, you can't go and buy players but for me the players who have been here have conducted themselves exquisitely. I can't have asked for any more from them."
England's next fixture is on September 8 in the UEFA Nations League against Spain.