so why the devs never use 90% of the content for end game?

[SamsaraTrickstar]

Because this amounts to "Just do more work." Adjusting old content to scale isn't something that just gets done overnight. The work required to accomplish this would 1) mean that you're sacrificing new content for scaled old content, and 2) have to be re-adjusted every patch to continue to scale with growing stats.

the game is out for how much years? do it over time no one say give it to me now. but do it.

Yes, like the blue mage. With this job every player did thoroughly rediscover every little details of the overworld, going from some mobs to another, thinking with excitement "how come i did never see this place even existed ?" and "i wonder what this mob attacks are, maybe i will learn a good skill ?".

Just joking, everyone did watch at some guide to get rid of "exploration" and "hidden secrets" as fast as possible.

so because some people "cheat" we cant have nice things?