I agree that France profited from Belgium's mistakes to win but overall France is better, more consistent than Spain and has a better players.
France is a team of experienced players and they already won the World Cup 2018. Spain is a team of young players like Pedri, Gavi, Olmo and they just start to grow up and compete for titles.
It is impressive that Spain with those young players can play too good in two tournaments recently: Euro 2020 and Olympic Tokyo. Now they will play the UEFA Nations League final match. If they win it, their young players will have a good experience because it is never easy to play in any final match. It's too much pressure especially for young players.
Deschamps is under pressure to deliver a win with his team for France after being eliminated in EURO and the struggle they are facing in qualifications.. A defeat in this final game of Nations League, although it isn't an important one comparing to EURO, could mean the end of his career especially if Spain will humiliate them.
The title in this league will be a relief for Deschamps and France after the terrible result in Euro 2020. They were too arrogant in that tournament and were beaten by Switzerland. If they can win this final and take it to reunite the team, they will be a strong team in World Cup 2022.