Additionally the cards had actual utility where the rarest cards often had better effects than commons and decks would be built around these rarer cards to be used in a duel. For games like Fortnite where the items in the lootboxes are purely cosmetic, the kids who are playing know that they aren't getting any competitive advantages with different skins in playing. However this becomes a bit murkier in games like FIFA and Star Wars Battlefront 2, where the rarest items from lootboxes contained items that were better than those obtained through leveling up alone. The article says that "92 percent of the FIFA boxes are not bought with real money, but unlocked via football matches and are therefore simply part of the game of skill." which implies players can expect to get a reasonable number of good players to build a team with and a team constructed of said players on aggregate would not provide a significant competitive advantage.
My opinion is that players should spend time in games because they consider it to be fun rather than to be the best for the sake of being the best, and the in-game whales who spend the most $ on a game shouldn't be overpowered to the point where free to play players should feel they need to spend money to win.