Playing for years and not improving is a very common scenario. It does not matter if you are playing for 2 years or 20 years. A player that is constantly improving can beat any veteran easily. Same goes for chess. A 15 year poker grand master will beat 99.999% of chess players.
The difference lies in his preparation and not the number of years he has been playing.
Poker is a very costly game, unless you train and constantly improve you are going to be left far behind. Every day strive to become better, learn and improve!