The impact so far proves to be zero. Because all the teams understand that the Nations League was invented instead of the usual friendly matches. That's why everyone treats these matches as friendly matches, where the coaches have the opportunity to experiment. I think the situation with these competitions will not change, because every two years there are more serious competitions.
But in a way, this is also in UEFA's interest, as it could make smaller teams able to increase their level of competitiveness.
That is, for France, Portugal, Germany, Italy, it may not be of much interest. But for smaller teams, it could be a good opportunity.