If a new player were to join, they will always be behind, and imagine if that gap is 10 years. This will turn off many new players.
Imagine a new player seeing content for season 20 on social media, then learning they need to go through 19 seasons to catcup.
There is nothing wrong with putting everybody on the same season. Just split us into different servers based on player power.
And New players can join New player servers. Or, even be able to join advanced servers through invite. Perhaps some players have the money to invest. PERHAPS, give new players a juicy starter pack.
But the message is, just put everybody on the same season.