Agreed. I think alot of international managers for a long time have fallen into the trap of trying to get all of their best players in.
I do think at tournaments the whole squad needs to be used, the top managers do this. In the last Euros spain used every player in their squad, Southgate had a fair few that didn't play a minute. And other tha were lucky to get the last 10 mins.
So, just because they don't start doesn't mean they don't have a role to play. Southgate ran a few players into the ground in the last few tournaments by hardly making any subs, Walker in the last euros springs to mind, he was exhausted by the final. Which is even stranger when England have amazing depth at right back.
Those great players that miss out can play in their proper positions when needed. Or even fill in for someone in an okay position for them for 30 mins or so. But unfortunately for them they just don't start when everyone is available.
An interesting fact I heard whilst watching the French match yesterday. Coman has over 60 caps for France and he's never played a full 90 mins in any of them lol.