I don't think this competition is a true indicator of the strength of national teams, and coaches should be too worried.
It is obvious that most of the main players of England, France, Italy ... came physically and mentally exhausted to this competition and were not at the right level for these matches.
Southgate still has plenty of time to prepare his team well for what is really the only thing that matters and that is the World Cup in Qatar.
I don't think anyone takes this competition too seriously.
I agree with you that this competition is not the main focus for the top teams, however it gives some indication in what state the national teams are. I don't think the exhaustion argument is valid much here. The World Cup would normally have happened now without long break before. Also in November the top players won't have a long break before the actual competition. France and England especially should see the performance of the last games as a warning sign, they need to come up with a good plan now.
it seems so, it is clearly seen by the number of rotations of players in each match. The big teams in this tournament don't seem to have more motivation to win the game, instead they are looking for a good position or squad to look at the world cup in the next few months.
The fatigue factor of the top European top players who have just finished competing in the league I think is not the reason but rather the priority of the national team which is slightly lacking in this UEFA National League tournament.
With this competition, UEFA has actually prevented national teams from choosing their own opponents and preparing in their own way for major competitions such as the European and World Cups.
Instead of one or two preliminaries as before, now the national teams have to play many more games in a very short time, which brings UEFA much more money, but this system of competition is not liked by players or coaches because it is too hard and the competition itself is not too important.
I heard a rumor recently that UEFA is planning another new competition, in which the winners of continental competitions would reportedly play. This all together becomes ridiculous, I guess UEFA will start a new competition every month just to make more money