Southgate's side face a winner-takes-all UEFA Nations League clash with Croatia on Sunday that will give some idea of how far they have come since they lost to the same opponents in the last four in Russia.
World Cup finalists Croatia beat Spain on Thursday to blow the Nations League Group A4 wide open, meaning victory for either Croatia or England at Wembley will seal top spot in the standings, and a place in the Nations League finals next year.
Such an outcome seemed improbable for England after they began their Nations League campaign with a home defeat to Spain and a draw in Croatia.
Yet a thrilling victory on Spanish soil has turned things around for Southgate's side.
England returned to a hero's welcome after their success at the World Cup, but Southgate believes that their form since shows they are still moving forward.
"We have learned with every experience that we've had," the England manager told reporters on Saturday. "We've added more depth to the squad in terms of young players and competition for places.
"We're always improving and I think in those five matches that you've seen since the summer, we haven't sat on our laurels.
"We want to keep improving and I think the players have shown that mentality."
Southgate said that the 2007 meeting between the two nations at Wembley -- when Croatia's victory ensured England failed to qualify for the 2008 European Championship -- will not be in his players' minds on Sunday.
"I remember the game and some of the players now were around at that time," Southgate added.
"That game has no bearing on tomorrow’s game. We have a completely new team and mindset.
"We’re trying to break barriers down and play in a different way and we’re getting better all the time.
"We are looking to win the match, it is as simple as that."
(Reporting by Peter Hall; Editing by Toby Davis)
