EXP nerfs in the current KMST Patch.

Precisely, having content to explore "all the way" to 250 would mean escalating that content to fit the game progress.

We have these 3 theme dungeons:
Mushroom Kingdom
Kerning Square
Chryse

Sweet content, right?
Not really.

Grinding will level you past that content so fast, that it won't be important anymore when you're level 60, 70, or 120. Because no level 70 will say "Hey, how about going to Mushroom Kingdom to explore the level 30 content?".

I've done all of those multiple times and I'd have to disagree because it's the same old thing once you've done it once and furthermore Chryse has a lot of what I would term filler quests which isn't fun for anyone. Note also that levelling up would still be far too easy during those levels so if at anything Nexon needs to work on good, long-lasting high level content and not screw it up after they make it (Remember PvP?). More areas like Root Abyss would be simply fantastic since re-visiting it gives you things to do, the bosses are worth fighting and you might even go there to find the occasional merchants while most of what we term as content now is only good for a look-see and some EXP before being dumped, simply because there's little reason to go back.