Your rank isnt affected by JUST getting better

You're rank is affected by getting better faster than your piers

Don't forget that every other person in your ELO is also gaining experience and improving at the game. In order to rise in rank you have to improve at a faster rate than them, not just improve period. Rank is not a static thing. Its dynamic and relative. Its 100% dictated by other players who are not programmed AIs. As the playerbase as a whole changes, ranks relative to each other will also change.

This is why "I know I'm better than 2 years ago but I'm the same rank" is a thing. Its not the ranking system being trash. It's working as intended. Ranked is a competition against other players. As those players change, you have to change with them.