I wish they would put the leaderboards in an easier-to-see place, like maybe put a Leaderboard with top 10 or top 50 near the gamemode (e.g. Solos lucky islands LB near the solos lucky islands portal), like with nametag thingies. You know, the ones that are always facing you.
If there was a monthly leaderboard, I would prefer the all-time leaderboard to stay, because a lot of people (including me) have put many many hours (even days!) worth of playing to get to where they are on the LB. If they would have to replace the all-time leaderboard with the monthly one, then I'd probably be fuming.
You could also just go for leaderboard on the new games, or just dedicate a lot of time/effort into a pre-existing one.