England will play further UEFA Nations League fixtures later this year when they face Croatia and Spain away from home in October, before hosting the Croatians at Wembley in November.
'It's been more enjoyable than 20 years ago, when I was nearly as famous, ' said Southgate, jokingly referring to his penalty miss at Euro 96.
The same 23-man squad will then play a friendly against Switzerland at Leicester's King Power Stadium a few days later.
Southgate has retained the bulk of the squad that finished fourth at this summer's 2018 FIFA World Cup, with 18 of the 23 keeping their places.
"It would be unfair to say he was happy as he wants to play, but he understands I want to see some young players in the shorter term", said the England manager, who was pleased to see Shaw back in the United first team.
England reached the semi-finals of the World Cup in July.
Regarding the ageing trio of Young, Cahill and Vardy, Southgate said their global careers were not necessarily over, but with the European Championships two years away he wanted to change the profile of the squad.More news: Apple plans three new phones
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Jordan Henderson and Trent Alexander Arnold return from the World Cup squad the valiantly made the Semi-Finals in Russian Federation this Summer. You're talking about replacing senior players with some 17-year-old's who haven't played Premier League football.
On the subject of Cahill, Vardy and Young, he added: "Those guys are older and - in a couple of their cases - aren't playing much with us". "If they have proven themselves as good as any other young players in the world, that opportunity has to be there".
'We had some mature conversations with Young, Vardy and Cahill and we have two injuries.
"We know what he can do and having got so close to the World Cup it's a bit early to bring him back into the fold".
"We wanted some continuity [but] we won't stand still".