Collection power is a really terrible way to determine a players' deck strength. Since gold foil cards have 50x the CP of regular foil cards, and all cards, even duplicates count toward the CP.
I tend to agree that bronze silver and gold leaderboards are a little strange, since it encourages people to stop leveling their cards and hang out there.
Maybe it should be like an achievement with no monetary prize. Like if you place 15th, you get the "🥉15th place Bronze Leaderboard🥉" badge. You could still try for a higher placement in a later season to earn a higher leaderboard badge if you want, or just take aim at earning a silver leaderboard badge.