Seasonal vs Eternal decision feels wrong

First time Diablo player - started a couple months back - love the game. Took a Spiritborn to level 270, Pit 110 before hitting a wall on content.

Just looking for some context on the seasonal vs eternal - specifically Blizzards decision to essentially make you start over if you want the new content. The idea of logging 150+ hrs into a character and having to start over makes me not want to continue playing. Am I missing something? Why can’t they add new content for endgame - like raising the level cap, adding more paragon boards/skill points, etc so you can keep leveling up? I used to play Destiny - where you essentially keep raising the ceiling and maintain your character…. This feels backwards to me unless I’m missing something…