"Arpad Elo's system revolutionized the way player ratings were calculated in chess and had a significant impact on the competitive chess world. The Elo rating system provided a more accurate and dynamic way of measuring a player's skill level, taking into account the strength of opponents and the outcome of games.

Arpad Elo's contributions extended beyond chess, as his rating system became widely adopted in other competitive fields, such as sports and online gaming. His work laid the foundation for modern rating systems used to assess relative skill levels in various domains."

Yes were all playing chess, you're playing checkers. A 6k elo player in chess is better than a 5k elo player in chess.
A 6k elo player in checkers is not better than a 6k elo player in CHESS. Its comparing apples and oranges.