You brought up two different problems. Content becoming outdated can happen for a plethora of reasons, the biggest one being the power creep via gearing. Even synced down, you're still hella OP for the content, and yes, that's a concern many players share. That's why things like Savage or specific extrema trials you still can't cheese even unsynced are appreciated. Nothing says 'aged well' like a full 370 ilvl party wiping to Sephirot because someone missed a tether.

As to the approach you described, you're going to find "must've cleared" or at least "must've watched a guide/know mechs" for extreme and savage content on release day. That's not a problem with the game, it's just jerk players.