In my mind, the top 20% are people who actually play. If you are stuck anywhere below that, you aren't even trying to improve. If a leaderboard says you haven't even cracked top 50%, then that leaderboard is definitely cutting players that don't play much from the bottom of that list. In most competitive games, the bottom 80% is just casuals who play a few times and stop, or people who only play the game while high.
Then the top 5% is when you start understanding the game at a competitive level. The very start.
Then the top 1% is where you can consider yourself good at the game, but, still, there are a ton of fairly bad players that play enough to get here but don't understand what they're doing. It's a combination of grinders and skilled players.
Then the 0.1% is where you have good players. Not pros, but definitely, unarguably, good.
Then you have pros.