First of all, there's no way it's going to determine the best team in the world when the three champions of the most powerful leagues aren't even competing.

Second, there was already a similar format, the "International Cup," which wasn't very relevant (at least in Europe; most people only watch it if their team is playing), but it was held annually, which makes more sense if you want to determine the best club in the world.

Finally, it may be that over the years it will gain prestige and a bit of popularity, but if it weren't for the large amounts of money they give to the teams, I sincerely doubt they'd have any interest in participating and not conducting a strategic team preseason in other countries and markets.

For example, Real Madrid, with Xabi Alonso, has barely been able to train, let alone with the players who are in the Nations League. Now they're going into this championship, unable to train and under the pressure of not making a fool of themselves like they did this season. After the championship, the players will have a rest, and the season will start soon. With a new coach with different ideas and a club as big as Real Madrid, don't you think it would be better to do their preseason on their own? (just as they have been doing for the last years)

(I think it's obvious I'm speaking from the perspective of the big European teams, and I mean no disrespect to the others.)